Story
The 1965 Plymouth Belvedere I A990 was a factory-built Super Stock race car, not a street-performance trim. Plymouth put the high-compression 426 Race Hemi into a lightened two-door post sedan on the standard 116-inch wheelbase. This page covers both factory transmission paths while keeping the altered-wheelbase A/FX cars separate.
A purpose-built Super Stock Plymouth
The A990 engine used 12.5:1 compression and a 425-gross-horsepower rating. Its magnesium cross-ram intake, dual Holley four-barrels, aluminum cylinder heads, water-pump and thermostat housings, and lightweight brackets reduced weight high in the car. Buyers could receive an A833 four-speed or heavy-duty TorqueFlite. Exact-package records report 101 Plymouth cars, including 12 four-speeds.
Lightweight without aluminum body panels
The body used thin steel and lightweight Corning glass, with aluminum door hinges and window regulators. Plymouth omitted the radio, heater, rear seat, armrests, much of the insulation and other passenger-car equipment. Unlike earlier lightweight Mopars, reviewed 1965 records describe stamped-steel exterior panels rather than aluminum fenders and hood.
Standard wheelbase is the boundary
An A990 Belvedere I retained the 116-inch B-body wheelbase, torsion-bar front suspension, rear leaf springs and hydraulic drum brakes. The small group of 1965 A/FX cars moved the axles and shortened the effective wheelbase. Those altered-wheelbase cars are important history, but they are not interchangeable with a standard A990.
Authenticate the whole car
The RO51 body code, A990 program paperwork, scheduled production record, broadcast sheet or IBM card, engine and transmission evidence, lightweight glass and hardware, paint and trim, and documented race history should agree. A Hemi, scoop, cross-ram, race lettering or altered stance cannot establish an original A990 by itself.