Looking for advice on correct bumper bolts. I don't know if year/model makes a difference, but my '70 Challenger currently has pan-head bolts on the front, and round-head bolts on the rear. Is polished stainless capped correct, or chrome, or does it really matter? What is the correct bolt size, 3/8-16 x 1", or 7/16-14 x 1-1/4"? Should the bolts use a nut with a free-spinning captured washer, or a nut with a serrated flange, or flat washer/split-lock washer with nut?