Is there such a thing as a car modifying program?

You all know how when you go to play most video games that you are capable of changing paint and tire and wheel combos. I would like to be able to do this with out the games but on my computer. Is there such a program to do this?Is there such a thing as a car modifying program?Not sure of the chassis end, but there are a number of dyno programs that you can put in the specs on motors and see simulated results.