yup, you can buy aftermarket odonnel heads, but his engines are modified versions of already existing engines. and honestly you dont want one anyway. the way odonnel does things, is he mods them, breaks them in himself before the event, and hands them to his drivers there. they run the event with it, and throw it away because its shot, due to his breakin process and running the engines very lean. the team drivers also get thier own blend of fuel too. i belive odonnel is the only guy that operates like this for offroad, this "throwaway" method is very common place in 1/8th scale onroad racing.