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1972 Plymouth Road Runner 400
For 1972, the Road Runner's standard big-block was Chrysler's 400-cubic-inch B-series V8. Sales code E68 and VIN engine character P identify the four-barrel engine, rated at 255 net horsepower and 340 lb-ft under the newer SAE net system.
The 400 could be paired with an A230 three-speed, A833 four-speed, or A727 TorqueFlite. A 3.23:1 8 3/4-inch rear axle was standard in the reviewed application table; the A36 package added a 3.55:1 Sure-Grip axle, larger radiator, fan, and shroud. Heavy-duty suspension and 11-inch drums were standard, with power front discs optional.
The cited forum transcription of Galen Govier figures reports 3,828 Road Runners with the 400: 1,433 three-speeds, 906 four-speeds, and 1,489 automatics. The numbers add correctly, but remain secondary-source attributed until a direct production reference is reviewed.
Twenty-eight named Road Runner exterior colors and six interior color families are recorded from the reviewed list. Road Runner emblems, Rallye wheels, vinyl roof treatment, paint, or an installed 400 remain context rather than proof of an individual car's original configuration.
For authentication, begin with RM23 and P in the VIN, then reconcile the fender tag, broadcast sheet, engine and transmission partial VINs, H400 engine marking, casting date, axle, paint, trim, and options. Satellite bodywork or Road Runner badges alone cannot establish a factory Road Runner 400.