The big problem that I see with trying to drop a V6 in a 5th gen or 6th gen ( correct me if I am wrong) none of the engine mounts line up for starters. So you would be re-welding engine mounts. Also the problem I see with the 03 6sp is that the tranny itself is bigger then a standard 5sp. I don't know to much about the 6th gen engine bay but I don't think without quit a bit of modifacation that you could stuff the 6sp tranny in there and not only that isn't the engine set in the 03 different then the rest of the gen's, seems somewhere I read that. Your best bet is if you want a lot of power get something new. If you want a moderate gain do the H22. The H22 will probably be your cheapest bet.