engineering prototype Grand Am was built and tested, but was later dismantled and destroyed. 1973 engines may have point or unitized ignition. 1974 engines may have point or unitized ignition or starting around May 1, 1974, HEI ignition. 1975 engines have HEI ignition. 1975 was the first year for the catalytic converter. 1978–1980 1978 For 1978 the Grand Am nameplate returned on a downsized model using the Grand Prix's G platform. It was offered in both two- and four-door models featuring a vertical bar grille and other trimmings to differentiate it from the LeMans, upon which it was based. Like the 1973-1975 models, this generation of Grand Ams also featured standard radial tires plus an upgraded Radial Tuned Suspension with front and rear sway bars. Interiors were similar to the Grand LeMans with either a standard notchback bench seat, optional 60/40 bench or Strato bucket seats with console and recliner on passenger side, an optional tachometer, and a choice of either cloth or "Morrokide" vinyl upholstery. Standard equipment included power steering, power front disc brakes, Turbo Hydra-matic transmission, full instrumentation and Pontiac's V8 engine with two-barrel carburetor producing . Optional was a 4-bbl version, along with numerous extra cost items such as snowflake wheels, whitewall or white-lettered tires, power windows and seats, tilt steering wheel, sunroof, and cruise control. In California, where more stringent emission regulations made Pontiac V8 engines unavailable since 1977, Chevrolet V8 engines were substituted including a standard V8 with two-barrel carburetor or optional four-barrel version with . 1979 Very few changes were made for 1979 other than the normal trim revisions and the demotion of the standard powertrain to a Buick V6 and floor-mounted three-speed manual transmission as standard equipment. The 301 V8, rated at with a two-barrel carburetor or with four-barrel, and Turbo Hydra-matic transmission were now optional. In terms of appearance, the only difference was that the park/signal and marker lenses were changed to amber ones. New for 1979 was a four-speed manual available with the 150-horsepower 301 four-barrel in 49 states. In California, only an automatic transmission was available and engine offerings included the standard Buick V6 engine with two-barrel carburetor and or optional Chevrolet 305 V8 rated at with four-barrel carb. The wood-grained instrument panel was replaced by brushed aluminum trim, while the gauge faces changed from silver with black letters and numbers to black with white letters and numbers. The same