I see you guys talking about PI head swaps and I also see that later years have PI heads.......so are these heads OEM heads?? Is'nt there any after market heads for the 4.6?? If so are the PI heads better than aftermarket heads??? I mean the 4.6 has been out since like '96 right?? I guess i'm just a little used to the LS1 slection of heads. I know the 5.0 has quite a few diffrent heads to choose from, so why not the 4.6??