if your trying to swap in a mod 4v engine like out of a cobra into a '05 mustang platform then it should fit like it was made for it, I think Ford planed for this from the begining, reason being the FR500 5.0 liter cammer and the 5.4 Shelby
if you do this do it to a V6, do you have modern computer controled engine knowhow? are going to do this for street or strip?