I would go with the Mitusbishi 3000GT (GTO) I believe that it is actually under the $50,000.00 mark, if you want to go over it, I say pick a Skyline. Anyone of the 4WD models, they all perform well, and are very quick, once tuned up.
The Camaros are a little heavy but so is the Mustang SVT Cobra. Hey, they're good and so are Corvettes. Maybe I'm just trying to defend the domestics (I live in the USA) but just try them out. The S2000, any Lancer, and a WRX are worthy choices too.
It all depends on what you want ! An FF car FR MR convertable 4WD class ABC
If you want a good car get an Integra soup er up and race. How far in the game are you. If you are in the amateur leage go to the American race and race til you get the camaro race car a few times and you will have some serious cash to buy any car you want!!