This is one of my favorite series in the game, blasting those production supercars all over the place is great fun. As such I've done it in a Ford GT, the McMerc, the saleen and a zonda.
All of those can win stock and make it a good race.
Also the M5, Callaway C12, Z06, and Spyker C8 are all fun to stick in there (they need a bit of tuning to get in and trying to keep up with the Cien in the Spyker and the Callaway was a lot of trouble)
For sheer laughs though, it's all about the TVR speed 12. Stock it'll destroy everything but then I tuned it to 1000+hp, Stage 3 weight, stuck N1 tyres on and turned of all the traction control (normally i leave the TCS at 2, the only car that I think needs a bit) .................
Wheelspin to 6th gear...............260mph............brake.......turn in.........skid out......massive spin.........hit wall/Dirt.............crawl brack to track sliding all over the shop......rinse...repeat.
Still came first at Seoul and New York, LMAO.