I have a 73 challenger, cut my rear brackets and welded to push the bumper in. I have about a 1.5" gap between the top of the bumper and the bottom of the tail panel. Do I need a metal filler like used on the 70's? I read somewhere that the 73 tail panel flared out at the bottom to reduce the need for this filler. If I shift the bumper up by widening the bracket hole, I'm afraid the valance then won't line up. Is this common?