I installed Hooker Headers and Sidepipe to my '79. They were purchased from Jet-Hot who coated them. The coating reduces the engine compartment heat. I think it's less than when I had the cast iron manifolds.
Charlie

Have you junked all the emissions equipment? Do you have any photo's of the finished set up as I have been thinking along the same lines for my 79 but not sure what it would look like, it is either sidepipes or the chambered dual exhaust system I was looking at. My cars got a 4 speed manual box, aircon, and the emissions pump, did the kit fit easily or did you have to make things up as you went along?