A 1976 Buick LeSabre is the car of John Gisberts. The exhaust pipe is on the right of the car. In one shot (when his kids put a condom on the exhaust), it is moved to the left. Same for a yellow sticker on the back of the car.
A 1976 Chevrolet Impala sedan is used at the end of the movie by John Gisbert and his wife to chase their kids. The number plate changes from 00-MF-60 to 27-MZ-67 between shots.