Dual Exhaust Conversion

Looking to convert my 69 Barracuda w/ 318 from single to dual. Not adding headers. Looking online I see a lot of "header back" packages. Who is the best source for "manifold back" packages?
Bob, I have brand new never installed muffler hangers for a dual exhaust w/318. I bought the wrong size from Accurate Exhaust. Save $50 from me.

A body Muffler Hangers and B body.jpg