Are f4 and f2 rims swappable?

and if not a direct swap what kind of modification is needed to make the rims fit?

 

Not a direct swap, brake rotors are bigger on an F4 and the F4 doesn't utilize a speedometer cable on the front wheel so the hub width / spacing could be different.

You'd probably have to swap the whole front end to get an F4 wheel on there. Although I'm not sure why you'd want an F4 wheel aside from the floating rotors? The F2 wheel is much better looking in my opinion.