273 / 318 Exhaust Manifold Question

273 Commando / Charger engines were given everything to bump up torque, including the single 2 1/2 in exhaust. I have run both exhausts, HP 273 straight thru and 2 in duals, and did not notice any difference. No problem there, but I do agree about getting rid of the passenger side heat valve. I usually just remove the flapper and tap for button head bolts. He also is running a small hydraulic cam. Not sure what pistons / compression ratio. Check for real TDC and start timing at 10* BTDC then optimize. The 4 speed should be a huge plus for a 273. What is your rpm range / where is it's red line. All MOPAR small blocks are great but they are not the same, nor should they be set up the same.