Single pane vs Dual pane

stock hp 383 from a road runner was 335hp. Dart/Barracuda would be a little less I think because of the exhaust manifolds.

Mopar Muscle built one and made over 400hp with bolt ons but they need to rev like a small block. They started out by building a bone stock 69 383 right down to the stock exhaust, intake and carb and cam. It made 338hp. Then they ended up swapping a Comp Cams XE284H cam, A Mopar Perf. M1 single plane intake, A set of Hooker 1-7/8" headers and a Demon 850 carb. It made over 400hp. I'll try and dig out the mag.