Use the Commando 2.5 inch single exhaust with straight through muffler and resonator. Uses stock exhaust manifolds. See Accurate Exhaust or Waldron Exhaust. Pricey but you get the idea.
I used the stock "Hemi style" muffler. It's a little quiet. Dang, Lon (@lkopaska ) has the Accurite system on his 67 Barracuda. I wish I had a video. His sounds sweet with a performance muffler.
