Dogface, as was suggested in another post, ask your overheating question in the engine shop.
I also believe too much tailpipe after the mufflers causes excessive, obnoxious noise. I have generic glaspaks on my '56 (350 engine) with short downturns after. They are sweet and mellow. I wanted the same sound on my Suburban (248 with Fentons). I had the same mufflers installed with long pipes out the back. It was obnoxiously loud when at highway speed. I added two more mufflers near the exits. It is now sweet and mellow going down the highway and gets a good rapping sound going through the gears.
