so i blew a nickel sized hole in the # 3 piston of my f3 on my way up to laguna seca last weekend = (

parts to rebuild my motor are going to run $400 and labor... well... we all know how much that can run.

i found a guy selling a f2 motor in good condition and am considering the possiblilties of throwing it into my bike.

here's what i know:

1) the engine does mount to an f3 frame
2) i can bolt my f3 carbs and airbox on the f2 motor so that won't be a problem

here's what i'm not sure about (any helpful info will be greatly appreciated!):

1) can i use a f3 computer or do i need a f2 computer?
2) are the transmissions between f2's and f3's the same (gear ratios?)
3) f2's use a speedo cable that attaches to the front wheel to gauge speed... i'm not sure what sensor the f3 uses to gauge speed (maybe from gearbox)... so how would i get my speedometer to work if i use a f2 motor?
4) is there anything else i should be concerned about?