I used a maxed out Lancer Evolution Super Rally Car '03 to complete mine. I had the most trouble with the gravel courses for some reason. The car came from the UCD. The Subaru Imprezza Rally Cars and other Evos were good for the beginner/intermediate, but I needed the Super Evo to finish expert gravel.
The Pikes Peak car won't work for the ones that have to have "Rally" in the car name, but can't remember which race(s) those were.
P.S. - I found the snow races to be phenomenally easy, but those gravel races irked me now and again, until I finally beat them. 👍