Restoration phases — the twelve-phase 1968-1973 B-body sequence

Twelve-phase restoration sequence through the 1973 emissions-era run-out closure.

The 1968-1973 Plymouth B-body restoration carries a twelve-phase sequence that opens with the pre-build survey on the 116-inch B-body unibody (NOT a 1970-onward E-body 108-inch / NOT a 1964-onward Valiant A-body 108-inch compact) and closes with the 1973 emissions-era run-out. The 1973 model year is the run-out model year for the Mopar-side 116-inch B-body muscle-peak; the 1973-onward emblematic emissions-era dashboard card anchors the 1973-onward run-out clip. Each phase lifts paragraph-for-paragraph from the standing Mopar brand-hub reference. The twelve phases below are the on-disk restoration-guide chapter skeleton.

1. Pre-build survey & unibody inspection: Photograph the as-found unibody rails (B-body 116-inch NOT E-body 108-inch / A-body 108-inch compact), the engine-bay cross-bracing on the Road Runner / GTX / 1969-onward reinforces, the partial-VIN dash stamping on the driver-side dash, the fender tag (model-code line 1 / body style line 2 / engine code line 3 / transmission line 4 / paint code + sales codes line 5 / trim line 6 / build date line 7 / DSO line 8 / sequential VIN), the door-jamb trim tag with the cartoon-horn callout on the Road Runner / "GTX" wordmark on the GTX / volume faceplate on the Belvedere, and the 116-inch B-body assembly-plant discriminator on the fender-tag VIN fifth-character plant stamp (Lynch Road Kentucky / Hamtramck Michigan).
2. Teardown / disassembly: Strip the 1968-1973 B-body shell to bare; capture every trim-tag row on the 116-inch-wheelbase chassis as-found; mark the 1969-only N96 Air Grabber hood on the 1969 chassis (NOT a 1970-onward A38 Shaker); mark the 1970-onward A38 Shaker hood on the 1970-onward chassis; mark the 1971-onward reduced-output carryover dashboard card; mark the 1973-emissions-era emblematic dashboard card.
3. Bodywork & rust repair: Rear quarter wheel arch + trunk-to-quarter seam + lower-quarter trailing edge ahead of the rear bumper bracket + sail-panel belt-line rust. The 116-inch B-body rear quarter is taller and flatter than the Charger coke-bottle quarter; do not assume the Charger coke-bottle flare is on the Plymouth-side B-body. The Plymouth-side trunk seal is a single-piece extrusion with a taller fin that matches the B-body deck-lid shape (NOT a Charger-side seal).
4. Surface preparation: Epoxy primer as the sealer coat (zinc-chromate additive matches the Chrysler factory 1968-onward chemistry), urethane primer-surfacer as the blocker, 180-320-400 block-sanding sequence. The Mopar-correct 116-inch B-body schedule is the documented B-body schedule NOT the 1967 Camaro single-stage schedule. Mask the flight-paint stripe outline before any basecoat is sprayed on the RM27 / RP27 (1969 RM27 only -- the 1968 launch-year stripes are 1968-only).
5. Paint: 1968-1973 Plymouth B-body color codes stamped on the fender tag line 5: FE5 Rallye Red / GB5 Jamaica Blue Metallic / QQ1 Crystal Turquoise Metallic / Y3 Cream / TX9 Black / W1 White, plus the 1968-only launch-year colors on the 1968 GTX 440+6BB, plus the 1971-onward reduced-output colors (SB4 Silver / SB8 Dark Silver), plus the 1973-onward emissions-era colors (359 Dark Blue Metallic / SP1 Sidewind / TB4 / FY1 Light Yellow). Single-stage on solid colors, basecoat/clearcoat on metallics. Impact-stripe mask sequence is a 1969 RM27 / RP27 / RS27-specific procedure.
6. Engine rebuild: The 1968-1973 Plymouth B-body engine chain crosses four distinct Mopar engines: 383 Magnum 4-bbl on the standard RM21 / RS21 / RP21 / base Belvedere / block casting 2536130 / 335 hp / 425 lb-ft; 440 4-bbl on the RM23 / RS23 / RP23 / block casting 2536430 / 380 hp / 425 lb-ft; 440+6-Barrel N96 M-code on the RM27 / RS27 / RP27 (topped with three Carter WCFB-3445 two-barrels on the Six Barrel-only ram-air intake casting 3462341 / 390 hp at 4,700 rpm / 490 lb-ft at 3,200 rpm); 426 Hemi elephant-block on the 1968-onward RM27 Hemi / RP27 Hemi hardtop (2840180 short-block / 2843730 head / 425 hp at 5,000 rpm / 490 lb-ft at 3,500 rpm). The 1971-onward reduced-output carryover reduces 383 / 440 output further on the emissions-era 8.5:1 compression ratio; the 426 Hemi drops at end of 1971 model year.
7. Transmission rebuild: TorqueFlite 727 three-speed automatic (L engine code on the fender tag with console-shifter on the RM27 / RS27 / RP27 N96 M-code cars) and A833 four-speed manual (K engine code with Hurst pistol-grip shifter on the 1968-onward RM23 / RM27). The 1968-1973 B-body column-shifter automatic is the optional transmission code on the 1968-1973 B-body 383 4-bbl carryover; cross-reference the engine-code line on the fender tag (L TorqueFlite / K A833 four-speed) against the as-found chassis configuration.
8. Suspension & brake rebuild: Front torsion bars + front 10-inch disc brakes; rear leaf springs + rear 10-inch drum brakes on the standard 1968-1970 B-body, 11-inch drum on the 1971-onward B-body. Cross-reference the rear brake size at the 1968-1970 vs 1971-onward boundary; a 1968-1970 chassis running the 1971-onward 11-inch drum brake reads as mis-restored at the brake level.
9. Wiring harness & firewall bulkhead: Body-loom / engine-loom / dash-loom three-loom split is the documented 1968-onward Mopar B-body convention. The 1968-onward Mopar bulkhead connector is keyed differently than the 1967 connector -- the ignition-switch connector position differs, the dimmer circuit path is borrowed from a different source on each year. Mixing up a 1968 chassis with a 1971-onward harness is the documented post-restoration fire pattern. Rear loom runs along the driver-side sill channel; rear lighting circuit on a separate ground path bonded at the rear-quarter-to-trunk-floor seam.
10. Interior rebuild: Road Runner-only instrument cluster gauge block carries the cartoon-horn callout (Looney Tunes "Beep Beep" road runner mascot) and the "Road Runner" wordmark (NOT "GTX", NOT Charger "R/T"); GTX cluster carries the 1967-onward "GTX" wordmark faceplate; Satellite / Belvedere carries the volume Plymouth-side faceplate. The 1968-only launch-year cluster on the 1968 GTX 440+6BB is on a 1968-only stamping distinct from the 1969-onward GTX cluster. After 1971 the GTX lineup closure drops the B-body cluster-level GTX wordmark in favor of a Satellite-only B-body carryover cluster.
11. Assembly sequence: Frame-first, then engine, then transmission, then front suspension, then rear axle, then body mount, then interior, then rear window. Tighten front body mounts to spec first, then rear mounts, then validate the engine hoodline by closing the hood and measuring the hood-to-fender gap (4.5 to 5.5 mm on a clean restoration). The 1968-1973 B-body uses a six-point body mount layout -- three at the front frame horn, three at the rear.
12. 1973 emissions-era closure & deliver (B-body muscle-peak run-out): The 1973 model year carries the 1973-onward emissions-era hardware (catalytic converter / EGR / thermostatic air cleaner / 8.5:1 compression ratio) on the 1973-onward reduced-output 383 / 440 chain (250 hp / 320 lb-ft torque on the 1973-onward 440 4-bbl catalyst + EGR configuration). The 1973 model year is the run-out model year for the Mopar B-body muscle-peak; after 1973 the 116-inch B-body muscle-peak ladder closes. The deliver phase hands off the restored 1968-1973 B-body with the year-correct fender-tag prefix scheme (RM-prefix Road Runner / RS-prefix Satellite / RP-prefix GTX on the 1968-1971 window / RS-prefix-only carryover on the 1972-onward window), the numbers-matching chain on the partial-VIN dash stamping + fender-tag sequential VIN, and the 1973-onward emblematic emissions-era dashboard card on the run-out model year.

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