Cab & body
Body, sheetmetal, paint, interior & safety
The core recommendation stands: keep the cab on the frame and replace the whole rocker, cab-corner and brace chain on both sides, with DIY epoxy primer and a solid single-stage topcoat, a steel bed floor with a liner, buckets with headrests plus 3-point belts, regular Missouri plates with the safety inspection, and…
Prices below were pulled 2026-10-12 from search-result snippets and the few vendor pages that would load (cjponyparts.com, summitracing.com, jegs.com, lmctruck.com and classicindustries.com mostly block direct fetches). Treat every price as "seen in a search snippet on 2026-10-12", not a quote. Items marked (unconfirmed) I could not verify. Where I could only find generic cost-guide ranges, I say so.
The pick
- Good
- About $1,500-$2,500 for the structure and finish set, unchanged: rocker and inner panels and floor supports (RPK34 $84.99 as a 4-panel set to be gauge-checked, IRP12-V from $40.99, Brothers 04-291 $26.79, AMD inner corner $19.50), DIY single stage ($131.99/gal was an orange pearl; solids are SUM-UP301G/UP300G, price not captured; budget about $100-$130/gal) plus Eastwood epoxy ($349.99-$369.99), Herculiner corrected to about $90-$117, Kilmat about $50-$142 per 36 sq ft, Seatbelt Planet bench belts $344.95 (mixed 2- and 3-point), TMI bench $1,560.99. Excludes seals and glass.
- Better
- About $5,000-$9,000 (estimate, not a quote): braces from about $69.95 to $219.99 depending on vendor ($144.99 OER/Classic), CJ FLP51 floor $662.99, bed floor $899.99 (BFLP2) or CJ WBFK2 $1,479.99 with tubs, Prothane cab mounts about $85-$101, Second Skin about $5.56-$7.94/sq ft, glass and weatherstrip about $800-$1,500, TMI So-Cal buckets from $1,076.99 or Procar from $602.99 each plus brackets, carpet $223.07, headliner, LED tail lights $172.99, standard shop paint $1,000-$4,000 (generic guide, 2025-09-18).
- Best
- About $12,000-$25,000 (estimate, not a quote): full cab-structure replacement; AMD bed floor $1,339.99 plus separately bought 4-inch wider tubs, or WBFK2 $1,479.99 with tubs; Dynamat Xtreme whole cab at 2-3 packs of $239.95 (about $480-$720, about $6.67/sq ft); TMI Pro-Series bench $2,231-$2,874 or TMI door-panel and dash kit from $1,826.99; showroom-quality paint $5,000-$20,000+ (generic guide, no KC quotes); professional spray-in liner about $800-$2,000 (weak source); one-piece door glass $969.99.
Structure: do it properly, cab on the frame, no body-off. For a truck that will be a teenage car, replace the full rocker/cab-corner/cab-support chain on both sides, using AMD inner pieces where available (19-gauge, EDP-coated) and Classic Industries / LMC / Brothers for floor supports and floors. Budget roughly $1,500-$2,500 for a floor, braces, rockers and corners kit set on a "Better" path if the floor is rusty. Replace cab-mount bushings at the same time: Prothane 12-piece cab mount bushing kit CABMOUNT9 for 1973-80 C10 is $100.99 (MSRP $111.99) at CJ Pony Parts and $85.11 at Performance Online (search results 2026-10-12); CJ also lists complete 2WD standard-cab mounting kits (e.g. 42740732S, price not captured) if the bolts and spacers are rusty. For the braces themselves, CJ lists two front floor support braces per vehicle (CFSB2-V) and separate rear horizontal supports (CFS310); prices not captured. A frame-off or cab-off job is worth it only if the frame is rusty at the body mounts. I did not find a clear owner consensus that cab-off is required for rocker/floor work; experienced members of a gmsquarebody thread advised against doing rocker work with the cab off the frame, citing rigidity and door fit afterward (gmsquarebody, re-read 2026-10-12). So keep it on if possible, brace the door openings, and take measurements before cutting.
Vendor. LMC is HQ'd in Lenexa, KS (not Olathe); a third-party listing gives its retail/pickup location as 15450 W 108th St, Lenexa, with hours that conflict across third-party listings (9AM-6PM daily in this listing; Mon-Fri 9-6 / Sat 9-2 and Mon-Sat 10-6 in others; none read from LMC itself) and a call-ahead number of (913) 492-8756 (listing; lmctruck.com itself returns 403 to fetches). That is a low-quality source, so call to confirm hours and will-call before planning around it. If it holds, buying panels at will-call saves the roughly $30 per-panel freight one forum post mentioned and lets you eyeball sheet-metal gauge before paying (gmsquarebody thread, re-read 2026-10-12: "LMC wants about $30 each for shipping" on floor pans vs AMD about $9.95 for both; one poster mentions picking up locally). Use AMD for inner rockers and corners, and LMC/Classic for the rest.
Paint: Good-to-Better. Do bodywork yourself, shoot epoxy primer over bare metal, then either DIY single-stage urethane in a rented or borrowed booth or a mid-tier shop for the color. For a commuter that will be driven by a teenager, single-stage is more forgiving to touch up than base/clear. Treat shop quotes as a separate decision after the metal work is done. Skip wood bed floor kits for the daily; see below.
Bed: steel floor (or Brothers/CJ pine strip kit) plus spray-in liner or Herculiner. Real hardwood is attractive but demands re-sealing. A new steel floor plus a cheap brush-on liner is the best durability-per-dollar. If you want wood for looks, Bed Wood and Parts is the standard name, but expect $2,500+ for a finished kit.
Seats and belts: TMI So-Cal bucket kit with headrests (or Procar) plus a 3-point belt kit. For a future teen driver, head restraints and 3-point belts are the biggest safety upgrades available that do not change the truck's look. Either keep a bench and fit the 3-point kit ($344.95), or go buckets with headrests ($1,077+). If you keep the original bench, it will not have head restraints (stock 1977 trucks did not). Buckets plus center console lose the third seat; weigh that against how Walter will use it.
Registration and insurance. Build under Hagerty with Vehicle Under Construction or a similar collector policy while it is a project. Once it is a commuter, move to either a standard insurer or a multi-vehicle "agreed value" program that explicitly allows commuting. Ask Grundy and Hagerty in writing. Use regular plates plus the biennial safety inspection. Missouri's legislature considered repealing safety inspections in 2026 (HB 1838 passed the House 104-43) but the repeal was dropped before the session ended May 15, so inspection still applies, but the House added the repeal language to SB 1408 on the last day and it was stripped, with the program "spared for another year," so expect the repeal to return in future sessions; over a decade-long build do not plan around it either way (Aftermarket Matters, KSMU).
Why it matters
A 1977 Bonanza single-cab C10 is a 49-year-old sheet-metal structure that will carry a 454, a heavier-duty drivetrain, much better brakes and tires, and eventually a teenager. Everything else in this brief (stance, brakes, exhaust, A/C, cooling) bolts to or sits against the body, so the body gets decided first. Structure comes before shine. The common rust sites on these cabs are the cab corners, rockers, floors, and the box-section cab supports that tie the floor, the rocker and the cab mount together. Square-body cab-repair threads routinely treat floors, rockers, cab corners and cab/floor braces as one repair set (for example a 1982 K10 cab-repair thread on gmsquarebody). Verification note: the "almost always rotten" and "rot from the inside out" quotes that an earlier draft attached to that thread and to a Speedway article were not found when the pages were re-read (the Speedway article is also about 1967-72 trucks), so they were removed. Treat the general rust pattern as common experience, and judge this truck by pulling the carpet and probing. Those same areas are what hold the cab to the frame in a crash, so for a future teen driver they are a safety item as well as a cosmetic one.
The big-block adds three body-side issues. (1) Heat: a 454 with full-length headers and dual 3" under a single cab cooks the floor, tunnel and firewall, so sound/heat treatment is a real comfort item here, not a luxury. (2) Weight and torque: 540+ lb-ft through a TH400 or 4L80E loads the cab mounts and the floor-to-frame joints more than a stock 350 truck would. (3) Interior: the door-to-door bench and the stock 1970s lap belts are the weakest part of the truck for occupant safety, and they are the cheapest to improve.
Rules and insurance push the plan too. Missouri's historic-plate program allows only 1,000 miles per year of personal use, so a ~35-minute interstate commute rules out historic plates (MO DOR). Hagerty states "We only protect classic and collectible vehicles that are not driven daily," and its footnote says occasional pleasure use "does not mean use for daily driving to and from work or school, routine shopping, etc." (Hagerty, re-fetched 2026-10-12). So the truck will almost certainly be on regular plates with a biennial safety inspection and a conventional (or "agreed value on a daily") policy once it is a commuter. Build to pass inspection and to be safe, not to be a show piece.
Fitment & gotchas
- Year range. Parts say "1973-87" but 1981+ front sheet metal is different. Order front fenders and grille parts by "1973-80" for a 1977, and double-check any "premium" fender (FEN73-V is 1981-87 only).
- Low-hump vs high-hump floor. Low hump is the 2WD column-shift AUTOMATIC floor (this truck's factory TH400 setup); high hump is 4WD and floor-shifted manuals. So FLP51 fits a TH400 (and a column-shift 4L80E, which is a TH400-style case but longer; tunnel and crossmember fit still need a mock-up). A T56 Magnum does not fit a low-hump floor: expect cutting the tunnel and adding an extended high-hump cover (an extended hump cover exists for 1967-72 trucks; check one for 1973-87) before welding in a stock-style floor. Decide the transmission first. An earlier draft of this section implied a Turbo 400 needs more than the low hump; that was wrong.
- Cab supports. The cab floor braces and cab-mount supports tie the floor, inner rocker and cab mounts together (CJ lists front braces, two per vehicle, plus separate rear horizontal supports). The exact count of box-section supports per side was not confirmed; look at all of them first. They are often rusty and cheap to replace relative to the floor, and they carry the cab load.
- Lap joints. New panels create overlap seams. Apply weld-through primer between them and seam sealer afterward, then cavity wax inside. Re-open drain holes.
- Inner fenders. They rust at the front corner where the small brace is spot-welded; check before ordering panels.
- Fuel tank. The in-cab 20-gal tank ended after 1972; 1973-81 short beds (117.5 in. wheelbase, 6.5 ft box) use a 16-gal tank mounted IN FRONT of the rear axle; long beds (131.5 in. wheelbase, 8 ft box) take a different tank: 20 gal frame-mounted (Tanks Inc TM1A, CJ FT69, Holley 19-455) or a 25 gal behind the axle on 1973-80 trucks (CJ FT98) - bed length and the tank sticker must be checked first (see section 90, 2.14); for the short bed (CJ FT68, $109.99 at CJ per search result 2026-10-12; the earlier draft said "behind the axle," which was wrong). It sits under the bed floor, so fix the bed crossmembers before dropping a new tank or fuel cell (CJ tank listings).
- Seat belts. Kits reuse the original floor-side mounting holes; you still need a B-pillar upper anchor bolt (about $7 each per the thread), and a longer shouldered bolt may be needed if trim is in the way so the swivel does not bind. A 1974 C10 in that thread already had threaded holes behind the trim for shoulder mounts, which is encouraging but is one example, not proof for every 1977; check yours. Check thread (SAE vs metric) before buying (gmsquarebody thread, re-read 2026-10-12).
- Procar seats need separate track brackets; TMI kits include them. Confirm seat width against a 60" cab: buckets plus a console need roughly 40-42" of the 60" bench space (my estimate, unconfirmed).
- Window and door seals. Rear-door beltline items (WSBL50) look like crew-cab parts; confirm against a single-cab door before buying.
- Tail lights. Sequential LEDs may need a flasher or load resistor, and the turn-signal circuit is part of the wiring section.
- Third brake light. There is no factory provision on a 1977 single cab, and no fitment-specific kit surfaced. Plan on a universal LED lamp at the rear window or tail of the cab.
How it touches other systems
- Exhaust (headers, dual 3"). Heat on the floor and tunnel is the reason to spend on deadening and a heat barrier. Do the floor repair, the insulation, and then run exhaust; leave a gap of at least 1" between pipe and floor. Headers and the steering box/column clearance are covered in the exhaust and steering sections.
- Transmission (TH400 vs 4L80E vs T56). The stock low-hump floor was built for the column-shift TH400, so TH400 needs nothing. The 4L80E is longer than a TH400, so mock it up before welding a floor in. The T56 does not fit a low-hump floor and needs tunnel modification or a high-hump/extended cover. Decide before buying or welding a floor pan.
- Brakes and booster. A larger booster or hydroboost pushes into the firewall and the cab-mount/brace area on the driver's side. Do not seam-seal or paint the firewall before the brake and pedal setup is settled.
- A/C and heater. The A/C box and evaporator sit in the firewall and under the dash; install deadening around them after the HVAC fit, and plan for a new dash pad only after the dash is finished.
- Wiring. LED lights, third brake light and a modern fuse panel change the rear harness. Bring that decision forward before the bed goes back on.
- Tire size and tubs. Big meats in the rear: wider mini-tubs (WBFK2, which includes them, or AMD 106-790-4073-64S, which requires separately bought 4" wider tubs) add clearance but limit the bed's width between the wheel wells. Settle tire size and axle width (tire and axle sections) before buying a bed floor.
- Fuel cell / in-tank. The tank location is under the bed floor, so the bed floor, crossmembers and fuel system are one job.
- Rear axle choice. A Ford 9" or a 14-bolt changes axle width and mounting; any narrowed or widened axle changes the wheel-well clearance. That affects the tub choice above.
- Insurance and plates. Daily use disqualifies Hagerty and historic plates; the owner's commute plan drives the whole registration decision.
Check on the truck
- How rusty is the structure? Pull the carpet, check the floor, inner rockers, cab corners, the four cab supports and the cab-mount bushings, and check the frame at the body mounts. Photos of each would let me firm up the repair scope and the cost.
- Is the bed a fleetside or a stepside (or something else)? Bed floor, bed wood, bumper and tail-light choices depend on it. Short bed or long bed?
- Do you want a bench (three seats) or buckets with a console for Walter?
- Does the truck currently have front shoulder belts or only lap belts? Is there a B-pillar anchor boss? I could not confirm what the factory fitted on a 1977 single cab.
- Where would you paint it, and how much of the work do you want to do yourself versus a shop? Do you want a factory color or a custom one?
- Is the truck currently insured, and with whom? Is it running on regular plates, or parked?
- Will it be the commuter from the start, or only after the build? That decides Hagerty versus a standard policy.
- Do you want to keep the Bonanza trim (and the badge) or change it?
- Confirm with LMC (Lenexa) by phone: will-call hours, which panels are in stock, and whether they can price-match.
- Ask your insurer whether sequential LED tail lights and a non-original brake-light layout are acceptable.
Fact-check notes
Adversarial pass, 2026-10-12. About 45 URLs were fetched or checked through search results; roughly half of the retail pages (CJ Pony Parts, Classic Industries, Jegs, Parts Express, Summit, Walmart, lmctruck.com, NHTSA, ck5, 67-72chevytrucks) return 403 or a CAPTCHA to WebFetch, so those prices were re-confirmed through search-result listings rather than the page itself.
Prices re-confirmed (unchanged): CJ RPK34 $84.99; FLP51 $662.99; IRP12-V from $40.99; Brothers 04-291 $26.79; AMD 481-4073-L $19.50 (page fetched); Eckler's EK-61-285433-1 $179.99 (out of stock); CJ WBFK2 $1,479.99; AMD 106-790-4073-64S $1,339.99; WSH16T $309.99; TMI SEAT362-V $1,560.99; TMI SEAT379B1F-V from $1,076.99; Procar SEAT76-V from $602.99; Seatbelt Planet $344.95 (fetched); TLLED233 $172.99; Dynamat 10455 $239.95; Summit SUM-UP362G $131.99; Eastwood OptiFlow epoxy kit $349.99/$369.99 (and $359.99 gray on eBay); Missouri historic plate fees and 1,000-mile limit (DOR page fetched); Hagerty VUC 10%/quarter, $25,000 cap, $750 tools (page fetched; the value increase resets each renewal and must be requested and approved); Missouri safety-inspection repeal died May 15, 2026 (Aftermarket Matters fetched).
Corrected:
- Herculiner HCL1B8: $72.25 not reproducible; now about $90-$117. Walmart link (CAPTCHA) replaced.
- Carpet $214.13 to $223.07 (page fetched).
- Dynamat Xtreme works out to about $6.67/sq ft, not about $5. Buying 2-3 bulk packs at $239.95 is about $480-$720 whole-cab, so size the cab area before buying rather than using a per-sq-ft rule of thumb.
- Kilmat, Second Skin and temperature ratings: the cited comparison page (gilroyblackout.com) is a window-tint blog, so those figures were removed or replaced with listing ranges.
- Summit SUM-UP362G is an orange pearl midcoat, not a solid single-stage; flagged and solid-color part numbers (SUM-UP301G white, SUM-UP300G black) added with price not captured.
- Paint-shop tier figures replaced with a dated source (Pickup Truck +SUV Talk, 2025-09-18); three spam or dead domains removed (caelum.com.br, kurlon.com, risingsunartscentre.org); the zarla.com link was Kingsley Classic Restoration's site, not "KC's Paint Shop".
- RPK34 is a four-panel set (2 outer + 2 inner), not one panel; flagged the suspiciously low price.
- Seat belts: Seatbelt Planet "i-30497563" is a URL id (SKU is 5009-V01) and the kit is a mix of 2- and 3-point belts; Brothers bench kits are driver/passenger only; RetroBelt priced ($179.99/pair) and found out of stock; a factory-style retractable 3-point option (CJ SBS30-V/SBS40-V) added.
- Fuel tank: FT68 mounts in FRONT of the rear axle (earlier draft said behind); priced $109.99.
- Low-hump floor statement was wrong. Low hump is the stock 2WD column-shift automatic floor, so a TH400 fits it; the T56 is the one that needs tunnel work.
- AMD bed floor 106-790-4073-64S only works with 4" wider tubs (bought separately); CJ WBFK2 includes them.
- Cost reference ($800-$6,000 and $600-$4,000) was not in the cited thread and was removed; the quote "corners almost always rotten" and "rot from the inside out" was not found at the cited thread and was removed.
- Classic Industries/OER brace $144.99 kept, but vendor range is $69.95-$219.99 depending on which brace.
- LMC will-call: hours unconfirmed (three conflicting third-party listings, see section 19); phone (913) 492-8756. Cab-mount bushing price (was "unconfirmed $50-$100") is now Prothane CABMOUNT9 about $85-$101.
- Insurance and plates: Hagerty "not driven daily" wording quoted exactly; Missouri inspection fee confirmed $12 cap; repeal may return in 2027.
Added missing options: Prothane cab-mount bushings, CJ cross-rail floor FLP53 as an alternative, factory-style retractable 3-point belts, vendor spread for cab braces.
Not verified: every Brothers part price marked "not captured"; CJ glass, weatherstrip and headliner prices other than WSH16T; Procar adapter bracket part numbers; the exact count of cab supports; whether this 1977 has factory B-pillar shoulder-belt threads; local KC paint and bedliner quotes; the NHTSA interpretation text; the Grundy daily-driver policy. The recommendation (cab on frame, full rocker/corner/brace chain, DIY epoxy plus single-stage solid, steel bed floor with liner, buckets with headrests plus 3-point belts, regular plates with inspection, Hagerty VUC only during the build) still stands for a 93-octane, 65-70 mph commuter that a teen will drive in about 2042.
Sources 51
- cjponyparts.com (search snippet)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- ecklers.com (fetched)
- autometaldirect.com (fetched)
- classicindustries.com (snippet)
- cjponyparts.com (snippet)
- gmsquarebody.com (fetched)
- ck5.com (search summary)
- gmsquarebody.com (fetched)
- gmsquarebody.com (re-read; does not support the quotes once attributed to it; Speedway article removed)
- gmsquarebody.com (re-read; supports cab-on-frame advice and a ~$1,100 rockers+corners estimate only)
- gmsquarebody.com (search snippet, LMC floor panels)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- jegs.com (snippet)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- hausoftools.com (search result; Walmart link removed, CAPTCHA wall)
- costinsighthub.com (generic guide, weak; risingsunartscentre.org content-farm link removed)
- summitracing.com (snippet)
- jbtools.com (snippet)
- cjponyparts.com (snippet)
- pickuptrucktalk.com (fetched 2026-10-12; generic guide, weak; kurlon.com and caelum.com.br links removed)
- ebay.com (Kilmat listing, search result; gilroyblackout.com removed because it is a window-tint blog)
- secondskinaudio.com (search result; the old /p/car-sound-deadening URL returned 404)
- cjponyparts.com and parts-express.com (snippets)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- cjponyparts.com (snippet)
- cjponyparts.com and cjponyparts.com (snippets)
- cjponyparts.com (snippet)
- seatbeltplanet.com (fetched)
- cjponyparts.com (snippet)
- ecklers.com (snippet)
- gmsquarebody.com (search summary, 3-point retrofit)
- cjponyparts.com (snippet)
- nhtsa.gov (snippet)
- dor.mo.gov (fetched)
- ksmu.org (fetched)
- aftermarketmatters.com (fetched)
- mshp.dps.mo.gov and jerry.ai (search results; telletire.com removed)
- hagerty.com (fetched)
- hagerty.com (fetched)
- grundy.com (fetched) and 67-72chevytrucks.com (snippet)
- giftly.com (LMC location and will-call hours, weak source; rpmcanada.ca removed)
- cjponyparts.com (snippet)
- cjponyparts.com and cjponyparts.com (snippets)