When we first see Paul, he is driving a red Porsche 964 series 911 cabriolet with standard (visible) headlights. Moments later, when he arrives in Coventry, his car now a preceding generation Carrera series 911 cabriolet with a slant nose front end with fold-down headlights and a whale tail spoiler.
In the exterior shots, Jack is driving an older Cadillac convertible at the beginning of the movie. However, all of the interior shots of Jack in the car are inside a more modern hardtop car. Also, he has the high beams on (all 4 lights) but when the car goes over the cliff only the driver's side headlights are working.