Is it possible in r -factor to have random pace cars for the mod? kinda like NR2003 has in the sim. if so how could you do this?

Not that I'm aware of. You can have a line set-up in the GDB file that calls for a specific pace car and just have a different pace car at each track (but that would cause mismatches). You could also go in a change the pace car folder names physically to so it loads a different pace car (this wouldn't/shouldn't cause mismatches). If there is some other way, I have never heard of it, thought of it, or seen it. But that of course doesn't mean it doesn't exist...