From Wikipedia, which corresponds with what I've read about Vanishing Point over the years:

The car Kowalski is assigned to deliver to San Francisco is an alpine white 1970 Dodge Challenger R/T hardtop bearing Colorado license plate number OA-5599. It has a 4-speed manual transmission with a Hurst "pistol grip" shifter, controlling a 4 barrel/440 cubic inch "Magnum" V-8 engine. A total of five 1970 Dodge Challengers were supplied to Cupid Productions by Chrysler Corporation. Four were identically equipped with 4-speed, 440 engines. The fifth Challenger was equipped with a 383 engine and automatic transmission, and was used primarily on the camera runs. (On the 2005 DVD release, director Richard Sarafian commented that there were a total of nine Challengers used during production. However, in a March 1986 Musclecar Review magazine interview, both Barry Newman and stunt driver Carey Loftin concurred that there were only five).

The 383 car was also used as the tow vehicle in the crash scene at the end of the movie. A ¼ mile cable was attached between the Challenger and an explosives-laden 1967 Chevrolet Camaro. The tow vehicle was driven by legendary stunt driver Cary Loftin, who pulled the Camaro into the blades of the bulldozers at high speed. After the picture wrapped, only one Challenger was still in service, as the other four were virtually destroyed during production filming.

Despite the speculation of the police at one point in the film, the car was not supercharged or turbocharged, but naturally aspirated with the single quad (4 barrel) 440/375 horse engine. The Challengers used in filming came equipped with a 4.10:1 Sure-Grip (limited slip) differential and were not well suited for high speed running. To compensate, the cameras were undercranked in some scenes to give the illusion of high speed. Also some chase scenes had the high speed engine noises of the Bullitt Mustang over-dubbed in portions of the sound track.