My 1984 C20 crew cab had the factory 454 Th400 3.73 rear end. The Q-jet was rated at 800 CFM for that application. I got a consistent 10 MPG no matter what. I would put a good Q-Jet together, get rid of the headers and tune it as close as you can to stock.
I’m big on factory original too with the exception of this Frankenstein dad built. We used to have many heated debates about stock vs original. My argument being that you can wring more HP out of it but at the cost of longevity, expense and simplicity.
That said, I’m curious as to what the disadvantages of headers are? I always believed the common assumption that improvements to exhaust flow was a good thing for both economy and performance. I hope I don’t sound argumentative or unappreciative, I’m just curious about the advantage of going back to cast iron?
