I would like to see a Mustang, but not an older one, the newer one's are much better. I admit I'm a bit biased, I own 3 mustangs, and I love racing etc etc. Regardless I would love to see some V8 cars in the game. They're not as limiting as some of you may think, with the RPM redline and HP, especially the newer Mustangs. I own a '99 GT with a mongoose kit, and a '03 Cobra with a KB2.2. I run them both to around 7k, and the HP is very near the torque.
Anyways, cars I would like to see in the game;
SN95/S197 Mustang GT/Cobra
RX-7 RX-8
R32/S4 Vag
..too many to list.
I guess any V-8 Coupe. Myself I love V8 coupes, I would love to see some Mustangs, and/or Vipers, and even some BMW M3/M5 and Audi S8 etc etc. The new era of V-8 Coupes are extremely fast and competative. Although I mostly like VAG and Ford, I'm a fan of anything fun, and there's a lot out there I would like to see. Even just one V8 coupe would make me happy. 400hp/400torque, 180mph!!!