I agree 100%. It all has to do with cylinder head flow, cam, cubic inches, rpm operating range and intake runner length and taper. In a given rpm range there are usually 3 high pressure pulse wave increases that occur (this is why you may actually see a drop in torque for a hundred rpm during a dyno pull , then it starts back in the upswing again.)The way to benefit most is to choose the area that gives you most of the goodie in your most benificial range. To get the "bestest" size and length of primary and colletor tubes, you have to do lots of syphering . It's the same way when trying to figure a camshaft. We are actually (and have for awhile)studying the use of two different cam masters. Basically long runner/short runner cam profiles. It's basically like having two 4 cylinder engines, one with longer runners and one with shorter ones. You tune with cam for each application and have a cam ground to fit. Headers are done with two primary tube lengths in an application like that. They don't change as much as a cam does though. They are more cubic inch guided. I have talked to ED many times and he is pretty sharp and experienced and always helpful. What he doesn't find out from a computer, he can help with the experience he has. I haven't run a full program on our type crate engines for headers, we set it up for a set we use on our dyno already, but at a tad over 500 inches and with an edelbrock, you'll most likely want something in a 34 to 35" primary for optimum performance. Make no mistake about it, you can benefit from a stepped header. They are easier to fab, so I don't know why header makers don't push em more. It loves a 3.5 collector and exhaust too.