In the opening sequence, we first see Paul stealing a 1969 Plymouth Valiant with a single-piece front grill. 47 seconds later, he gets out of a 1968 Plymouth Valiant with a split front grill and a different license plate. In response to a You Tube comment, Sean Bury said in 2016 he believed they were rental cars and when the producers went back the next day, the first car had been rented out so they rented the closest model available.
The 1967 Ford Mustang that is stolen and crashed into a river or lake, had turned into a 1964 to 1966 type of Ford Mustang (the triple vertical tail lights are contained in one chrome structure, instead of being three separate lights.)