Just thinking out loud here....I would think that if Bill Fisher, for one, suggested the use of headers over the stock exhaust manifold, than it stands to reason that the headers would give you better performance.
As far as two piece headers go, I know there were Fentons, Clarks, Belonds (Clarks and Belonds looked the same) and Douglass. I have a set of Belonds and I have seen Nicsons for the Chevrolet inline six engine. Someone is now reproducing them. At lest one of our members has a pair.
Joe
