fairly common. The 1973 Nova with a six-cylinder engine or 307 cu. in. (5.0 L) V8 were among the last Chevrolets to be offered with the two-speed Powerglide automatic transmission, which was in its final year. A dressy Custom series (which became a mid-level trim package in 1975) joined the Nova line and a Custom hatchback listed for $2,701 with a six-cylinder engine. That was $173 more than the six-cylinder base-model two-door hatchback. Air conditioning added $381. Every 1973 Chevrolet Nova got side guard door beams and additional sound insulation, as well as flow-through ventilation systems. A sunroof could be installed, and fold-down rear seats were available. For 1974, the Chevrolet Nova got a centered bow-tie grille emblem, as well as modified bumpers that added two inches to the length and helped cushion minor impacts. The Powerglide was replaced by a lightweight version of the three-speed Turbo-Hydramatic 350 ( THM 250 ) already offered with the V8, which was the only V8 offered for 1974. Nova sales continued the surge they had enjoyed since 1972 and approached 400,000 cars for 1974. Six-cylinder Novas were the fastest gainers, as sales of V-8 Novas declined. These were the years of the first energy crisis as Middle Eastern countries cut back on oil exports. After waiting for hours in gas lines and fretting about the prospect of fuel rationing, thrifty compacts looked pretty good to plenty of Americans and it fit the bill. The 'Spirit of America' Nova was introduced in 1974. In anticipation of the US bicentennial in 1976, the limited edition Nova Coupes were painted white and featured blue and red accent stripes as well as red and blue interior carpets and fabrics. Oldsmobile and Buick entered the compact car market; both the Apollo and Omega debuted, using the same body styles from the Nova lineup. Additional options were included on these Nova-like models, such as lighting under the dashboard and in the glove compartment. Pontiac's final GTO of this era was based on a facelifted 1974 Ventura coupe, itself based on the Nova, but fitted with a shaker hood scoop from the Trans Am. Novas and all 1974 cars were fitted with a weight-sensitive relay within the front seat that prevented the vehicle from being started until the driver's seatbelt had been fastened, following a safety mandate from the NHTSA. Later, Congress repealed the mandate requiring this type of device,