A 43 inch primary???? I would run exhaust manifolds first.
That header is 60-70...who knows, could be more depending on your combo HP off a good set of headers.
I'd look and see if TTI makes an under chassis header. I'm not sure if the Headman header is under chassis/some tubes out the fender well but if it is, that would be better.
I can't think of a scenario where a primary tube length of 43 inches would ever work. Maybe, maybe 38 inches would be ok. 34 would be better.
