You can't compare a Thermoquad spread bore carb too a square bore carb. The primaries are tiny and the secondaries never fully open on a stock or mildyly modified motor. Those big carbs worked only because of the small primaries.
CFM......cubic feet per minute, a measurement of the velocity at which air flows into or out of a space. I was talking air not fuel... the fuel can be adjusted.
I'm not going to argue with you on this. Run the small carb I really don't care. I would take the larger carb (750) on a 408 come race night everytime. Don't believe everything you read.