Plenty of carb CFM calculators out there. Here's one...
http://www.4secondsflat.com/Carb_CFM_Calculator.html
They compute that a 200 CID Model A at 3,000 RPM needs about 150 CFM. If you try to supply much more than that you could have some drivability issues.
Dual carbs are pretty cool, however
, and I would personally try to make them work. Use the smallest CFM carbs that fit the manifold, longer duration/higher lift cam, higher compression, play with jet sizes.
Good luck!
