My buddies 2007 YZ450F had a somewhat catastrophic cylinder head failure, I haven't had a chance to check it out yet but it sounds like he has at least three bent valves and a shim bucket that is broke in half along with some other assorted damage. I'm scrubbing Ebay looking for a replacement for now, but need to know which year model YZ450F heads will fit the 2007? Which year WR450F cylinder heads? Will YFZ450 cylinder heads from the quad fit, and from which years? Thanks.