You could cut or grind the bit of body seam matt-brown is talking about or you could bash it up with a hammer. If you don't make room the exhaust will hang lower on the RHS.
There is a place over here that does exchange bumperettes with the cut out and painted colour matched, but they are about $250 ish. Just cut the plastic out your self if you have a jig saw, make a template of the other side with a bit of cardboard, flip it over and trace it onto the RHS.