And the reason you prefer manifolds to headers is what??? Maybe noise??? Or some other reason, and what might that be, please?
I have manifolds on my car, and 2" pipes to the back bumper, with Flowmasters just ahead of the axle. The car is a cruiser, not a racer. To my ears it's just about loud enough, but still pretty sweet sounding.
My project car will be louder, anyway, with a 360 and a "fairly warm" but streetable cam and a low rear end ratio Sure Grip for acceleration giggles. Probably won't even bother with putting a radio in it, and noise won't be a factor.