Go to the effort to plumb the manifold floor with exhaust heat- - - -it's worth it for good performance through the entire operating range. The best way to do this is to use an OEM exhaust manifold WITH A HEAT RISER and do the "split" that people in the know have been doing for 75 years or more. It's not just a matter of adding a second pipe- - - -a baffle is installed that almost (but not quite) separates the manifold into two separate chambers. A small gap is left at the top to allow a small volume of exhaust gas to be shared by both sides. Like P.T. Barnum, "Fenton" knew how to reel in the suckers. An inline six engine needs either ONE, or THREE carburetors- - - - -not two!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!