Yes you can put pistons from any motor into another motor just have to bore out the cyl. if there is enough cyl. material to bore out.NO you cant put the F20 head on a K20a block, one uses a timing belt, the other uses a timing chain. and they also spin the oppisite directions so the cams, vtec sylinoids ect are gonna be on the wrong side. Sorry to bust your bubble but what you wanna do is a no can do its like putting a Kseries head on a Bseries block, it just dont work.