I put headman headers elites on my 454. 1985 325. I payed extra for the ceramic coated ones. It hasn't left the driveway, and they are already rusting. The ceramic coating is nothing more than silver heat paint. I'm not impressed. I thought they would look like stainless. They looked like silver paint. Better to get unpainted or black. Sandblast them, and paint them gloss black engine paint.
Call the guys at summit, to make sure the headers you want ,will fit. Exhaust ports could be square or round. Just for grins, weld an os sensor bung on the bottom by the collected. That way when or if you want to put a Tbi carb on, you won t have to remove or get under the coach to weld on in.
Hope this helps. DJ