The 'Coyote' was a kit-car for the pilot and first two seasons. It was in actuality a 'Manta Montage', a fairly popular kit car available at the time. There were a couple of minor body modifications to disguise it, but it is plain to see what it really is.
It was powered by the new-at-the-time Chevy 2.8L V-6, which was a fairly sophisticated engine for it's time. This is the same engine that came in the Chevy Citation X-11.
Brian Kieth, being as overweight as he was, clearly found it next to impossible to climb in and out of the Coyote easily and the scenes were filmed in such a way that this was not emphasized.
The last season of the show, a 'DeLorean' DMC-12, the infamous stainless-steel, gull-winged sports car from John DeLorean was heavily modified to resemble the original coyote as close as possible. The heavy gull-wing doors were removed completely, and lots of fiberglass bodywork was created to disguise the fact that this was a completely different, much larger car. Mr. Kieth could more easily get in and out of it, so that was one big reason they switched.
Side by Side, the differences between the original 'Coyote' and the DeLorean-based model were clearly obvious, and when the show used existing footage of the original Coyote interspersed with newer footage of the DeLorean-based model, the continuity of the episode was shot all to hell!
The poster above mentioned that he thought the car was really a Porsche 917 race car. Not quite, but on the right track: The original car used for the Coyote, a 'Manta Montage' was a replica of sorts of the Porsche 917, although nowhere even close to the Porsche in terms of performance.
