I have a friend with a "99 YZ400f, it needs a new bottom end. There was a '98 YZ400f that sold locally near me that had a newer 450 motor (can't remember if it was 03-05 or 06-09) swapped in. I was under the impression that this was not a bolt in swap? the swing arm on the later bikes is different? can I just get a swing arm from one of those bikes and put it on my friends 400f? basically what all is required to put a later 450f motor in a 400f bike?