This is a stupid question, but is there a difference in the f2/f3 frames? Could I swap an f2 motor etc. onto an f3?

 

There are a few minor differences, but nothing to worry about. The motor will bolt right up. Some of the wiring connectors are slightly different, but thats pretty easy to fix. Also the shift linkage will have to get flipped over, still nothing to worry about.
I'm planning on doing the same thing next week.

 

I have a complete f2, but the frames garbage. I could just swap everything over?

 

Pretty much, the radiator mounting system is a little different, and some other minor things, nothing hard to fix.