I got one better for you. Win the CADILLAC CIEN '02 in the Rally d' Umbria race under Special Conditions. I modded the heck out of it and it flat out flies. Only spins the tires in first gear. Buy a set of Medium Racing slicks for it and you're set. It's still not easy but it will keep you with the lead pack if you can drive it.
Good post. I'm also wondering what would be good. I was thinking an M3 all pimped out. My dumb ass *thought* the Ford GT was NA but I guess it comes with a Supercharger. Poopy. I also thought about buying the ZR-1 Vette and going balls out on that sucker. It has the legendary LT5 engine (not that it matters in a video game)
I been using my m3 for just about everything, i used it for the N/A and had no problems. Infact i'm running it in the supercar right now won first 2 races no problem.
I'm a HUGE fan of the NSX-R Concept (which you win at some point). It's by far the best handling car I own with 0---zero---suspension/transmission mods. It sounds wicked too. (Not including the LM Camaro)
A Z06 Vette with 700 HP would also work quite well .