okay, first of all the 4.6l block is a totally different design than the 302 motors in being it is overhead cam. the gt40 and gt40p heads are meant for the pushrod small block fords, not the new modular motors. ford makes aftermarket 4.6l heads and there are other places that make aftermarket parts. if you want to find out some other 4.6l speed parts, check out this site
http://www.seanhylandmotorsport.com/index.html .