Two 1968 390 cu. in. V8 Ford Mustang GT Fastbacks (325 hp) with four-speed manual transmissions were purchased by Warner Bros. for the film. The Mustangs' engines, brakes and suspensions were heavily modified for the chase by veteran car racer and technician Max Balchowsky. Ford Motor Company originally lent two Galaxie sedans for the chase scenes, but the producers found the cars too heavy for the jumps over the hills of San Francisco. They were replaced with two 1968 375 hp 440 Magnum V8-powered Dodge Chargers. The engines in both Dodge Charger models were left largely unmodified, but the suspensions were mildly upgraded to cope with the demands of the stunt work.