What size header would you guys use for the following engine combo. It is strictly a race only engine. Car is a 73 Duster, fenderwells are not cut and I don't want to have to cut them. 408 12:1 Trick Flow 190 heads Victor 340 intake .550-.571 SFT cam (I know it's small, will probably get something larger down the road) 750 carb (have 850 that will try as well) Don't plan on turning the engine over 6500 rpm. Car weighs 3250 with driver. Currently I have a set of Doug's 1 5/8". Trying to determine if a larger tube size would help any or not.