Question about making mods

If I wanted to make a MOD for GP4, for example with street cars or a NASCAR MOD is that possible to do that. Not that I'm going to do that I was just a bit curious.If I did a NASCAR MOD would GP4 except the Stock Car body and oval tracks. Also if I wanted to do drag racing would I be able to make a drag strip and be able to use it in GP4.

1- Yes
2- No