It doesn't work that way.
People won't just make a mod for you. If you are interested in a mod, it is recommended to try yourself. I have been playing with just doing a reskin of Hoppah's LA mod, and that will teach you a bit. Then you can follow some of the tutorials on here about adding/changing vehicles, changing scripts.
Eventually, you might even get to the point of making your own models.
It's not easy, trust me. But the end can be worth it.