Ive searched and not found a diffinate answer. I have a 1998 mustang with a 2 valve 4.6 and suspect the valve guides to be gone. My brother has a good set of 5.4 2 valve heads off a 1998 expedition he said he'd send me, so im trying to figure out if they will work. From whet ive found and seen they appear to be almost identicle except the 5.4 has smaller combustion chambers a little more valve lift and about .015 bigger bore. So has any swapped them or know if they will fit???