no you have to change the entire front end not just the bumper if you go with the 4.8 front end.
But if you want it to look like a 4.6 or 4.8. Just add the lower front bumper spoiler the 4.6 comes with. the 4.6 bumber looks almost identical to the 4.8 bumper. the only diff is the 4.8 bumper and spoiler is one piece and the 4.6 bumper and spoiler are 2 pieces.