My favorite car and track comp. is the Alpine lmp2 around Watkins Glen Short. The track really flows well and with the lmp2 all the corners just seem to be the right speed.
I havent driven many cars or tracks yet but ive had a blast so for with the Ariel Atom v8, zackspeed capri and radical sr3 around Watkins Glen Short. I think that will be the track I use to set up the base settings for a car.
I had a crazy save in the Atom the other day. I got a little distracted and the second to last turn snuck up on me. Check it out in this short vid. (towards the end at 27 sec)