If anyone else here has a Sweptline with the 318 Poly (evenly spaced exhaust ports), there are fantastic headers made by MoparNorm at the Dodge Truck Association (DTA). I think the last year of the Poly was 66 but I've seen many 67's powered by a Poly.

I put a ceramic set on my freshly rebuilt 66 Poly engine, hydraulic lifters, 450 hp, and they are awesome!!

http://www.t137.com/dtapoly/addpoly.php