340 11.6 to 1 compression engine misses

I've been fighting the same EXACT problem for two years...changed and replaced many things....I have a 68 dart GTS 340 mild build such as yours...stopped by this old school mopar racers house one day( I didn't even know him) he was happy to take a look...took off the air cleaner looked at the 650 Holley and said " simple, the carb is too small...period" I'm like really? He said watch this...held his hand over the carb about 10" high...slowly moved it closer to the carb..At about one inch away....purred like a kitten in gear...for the first time EVER! Told me to put a 750 oh it and it would be fine...I did(that same day) and it is...needs to be richer he said....I was under the impression that that carb was way too big...try that out and report back... Just sayin...