Without reading all the previous comments (sorry)
I came up with these ideas.
* Maybe an rb4 WRC or group N rally car.
* Maybe a group B style rally(cross) car
* a fast group C style GT prototype
* Or an LMP1 and / or LMP2 style open GT prototype
* more classics! Like Alfa GTV's, Austin Healy's, Mustangs,
E-type's, Lotus cortina, Lotus Elan, BMW 2002 etc etc.
* a turbocharged singleseater like Champcar
* Saloon cars, and their WTCC style race-equivalent.
(They probably have been mentioned
before)