Making a stovebot cylinder head "breathe" is impossible. It doesn't matter what you bolt on before and after those horribly restrictive ports- - - -the reason sand flows slowly through an hourglass is a pretty good representation of a stovebolt cylinder head. Multiple carbs and any sort of header system at all is eye candy, as it does nothing that the original single carb and one pipe exhaust can't do better and for less money.
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!