yes it's possible, you just have to find someone willing to do it

What's the name of the file and what's the location of the file

There's two that I've found. One is "v_club_roc_micstd" and the other is "v_ilev_fos_mic"

it already exists in game, use object spooner to spawn it

It sounds like you don't have a legit copy of the game if you're asking for cars that were part of a free update

The Pickups mod kind of does this already

a 4 door mustang is blasphemy

http://www.mediafire.com/file/psc1ia89f0t4p4i/Hair.rar/file

For some reason I can't get the hair model to stay in place. I can successfully convert the model to ydd, but you'll need a more experienced modder to make it work properly