Mopar V8 left exhaust manifolds side by side pics

Use the 273 64-66 manifold. Make sure Waldron gives you a 2 1/4 muffler. They wanted to neck down my 67 Formula S exhaust to a stock 2 barrel muffler. Your muffler should be straight thru as well as the resonator. The stock Commando exhaust works great. Trying to use a 68-71 340 manifold will add a lot of headaches, clearance, custom exhaust, 273 ports vs 340 ports for next to no gain.