BBSD - the manufacturers (with the exception of Zenith) did not publish CFM ratings for these carburetors.
What one must do is homework. Measure the main venturi of a carburetor which was designed for a specific engine. Look at the fuel requirement curve for that engine, and how applicable it is to your specific needs. The Holley 94, as an example, has main venturi from about 3/4 inch to 1 1/16 inch depending on which Holley 94. The Stromberg 81/97 are special cases of the Stromberg EE-1 which have the same sizes as the Holley 94.
But don't feel you are limited to automotive carbs. Someone made a 4 1-barrel manifold for the 2 liter Pinto engine. We built one for a friend who ran one in one of the outlaw racing leagues. We used 4 Mikuni motorcycle carbs. The engine ran like a scalded dog! (So well that multiple carburetion was banned by that league at the end of the racing year)!!!
But if I were going to build a multi-carbed 235, I would want to look at the runner design in the specific cylinder head (are the ports siamesed, are all ports individual, do the ports come to a common point, etc); then, based on this information, look at what 2, 3, or 6 carb manifolds might be available, and look at their port arrangement. The idea is to have each carburetor flow equally into either 1 (6 carbs), 2 (3 carbs), or 3 (2 carbs) cylinders. One wants to avoid an overlap, where 2 carbs are feeding into the same cylinder (this is why tripower doesn't function as well on a V-8 as either a single 4 or dual 4's).
Once one has decided on a cylinder head/manifold combination one can then pick carbs to feed the number of cylinders desired.
I really like the looks of the Corvette 3 1-barrel unit, but I understand clearance may be an issue in some trucks.
I also might try to do 6 1-barrels, fab the manifold (it is really fairly simple to do so using a piece of 3/4 inch sheet aluminum, various electrical conduit bends, and some flanges off some junk carburetors; and then use maybe 6 small engine carbs (Onan generator, motorcycle, etc.).
In manifold fabrication, it is very important (except for all out racing) to run balance tubes from port to port allowing the pulses to even. Trying to do 1 barrel per individual cylinder without pulse control can be a nightmare.
To synchronize multiples of 3 or more, begin with the center carbs, and syncronize the outers to the center.
I personally use solid linkage (all carbs functioning at all times), as I feel this works the best for a street engine. For a race engine, one can use progressive (idle or pace speed on one carb, and everything when wide open).
Jon.
