The 72 Rallye rear panel would be a semi-gloss (almost flat) non-textured black. Trim Black from Penstar is good for this. They are on the web at
http://penstar.bizland.com/ Their textured argents are very good as well as are all their other trim paints. I would stay away from their engine paint and stick with MOPAR's product - I didn't have much luck with it.