There Are Some Original Cars Left
Out of the original 10 or so vehicles used in shooting, only a couple survived. Almost all cars used for stunt scenes were scrapped for obvious reasons. However, vehicles that were used for promotional shots, driving scenes, and so on survived (via Auto Evolution).
On the other hand, it is very easy to make a replica of the ‘Starsky and Hutch’ Gran Torino since the modifications are easy to duplicate. However, the original cars have documentation which shows that they are the real deal.