Mike,
Your forgetting the efficiency factor in your calculation. Most engines run 80 to 85%, with real good intake, cam profiles, heads and headers you can reach 90 to 95% but thats about it untill you go to forced induction.
Your 743 CFM X .90 = 669 CFM. 743 CFM X .95 = 706 CFM
Go to
www.csgnetwork.com and plug in the numbers. It does the calculation for you. Two 500 CFM Edelbrock's, progressive linkage, lots of power with no flat spots.
Ray