63k for rfactor, hmmm i doubt that it could run 4 cars smooth. Rfactor can't handle high poly models very well. Up to 35k tri's and not to large texture size will do for a full field of cars. But 63k is really a killer. You can run only very few cars at the same time and you have to limit the textures will it ever be playable. I think you are going to have very many lods here
But about the model, it's simply amazing, very very good and clean. Nothin to crit on except for the thigns tom mentioned, and the wheels are a bit too small.