Jim Hall's Chaparrals were fantastically advanced for their time - the 2D and 2E cars were the first race cars ever (pretty much) to have two-speed transaxles, the first cars to have adjustable wings, and so forth - the 2J was the first ever (and really the only) Can-Am car ever to have ground effect - it was killed by its competitors (Teddy Mayer of McLaren, mainly) after its first season as they realised it'd kill its competition completely with a little development. Jim Hall was so disgusted by this that he quitted motorsport completely after it happened.
Chaparral were one of the most innovative and exciting makes in American motorsport and I'm very happy that PD made them such exciting and characterful cars in GT4. The 2D, for example, has a massive top end, but is like a tractor at low revs (in sound and speed terms) and is challenging for this reason. The 2J is just cool. I like them a lot. 👍