From what I've read, it was either four or five Challengers. Either three or four were 440 Magnums with four speeds (at least once, a 440 badge on the hood is clearly visible). The other car was a 383 Magnum with an automatic. The automatic was the one that was used to tow the Camaro via a cable into the bulldozers and was frequently used as a camera car.
Also, note that despite the obvious display of Chrysler products in addition to the Challengers in the movie, there is no "Vehicles Courtesy of the Chrysler Corp." tag at the end. Also from what I've read, when Chrysler discovered that the movie involved a guy taking speed and even featured a nude chick on a motorcycle, the decision was made to disassociate the corporation from the film. Stupid move, as "Vanishing Point" undoubtedly sold more Challengers than all of Chrysler's advertising put together.
