Since the integral-intake cylinder head isn't particularly popular, a little machining and tinkering on it to adapt a small-bore Rochester 2 barrel carb calibrated for a 265 V8 might be a better option than the current Q-jet setup. I doubt if you'll ever get it to wind up tight enough to open those massive secondary barrels, and the acceleration stumble probably means it's going lean even on the primaries unless you feather-foot the gas. I also seem to remember Rochester making a 2 BBL for some of their 90 degree V6 engines in the 1980's that was essentially the front half of a Q-jet with no secondary barrels.
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!