Slotting the throttle body mounting holes only increase the number of manifold on which the carburetor may be mounted; NOT the different displacements on which a carburetor may be used efficiently. The internal main venturi diameter places limits on efficient use.

We have advocated for years when migrating ONE carburetor for one engine to another STREET ENGINE that, FOR BEST RESULTS, the "donor" engine should be +- (plus or minus) 3 percent in displacement from the "donee" engine.

As example, Chevrolet made a 235 CID. 3 percent of 235 is approximately 7; so for best results, a single carburetor from other engines of displacement of 228 to 242 should be used.

Can this "rule of thumb" be ignored? Certainly, but results may not be totally desirable on the street. Example: we used to sponsor a 4 cylinder race team with a 2.0 liter (121 CID) engine from that company whose name is the same as the last name of Tennessee Ernie. For racing purposes, we installed a four-barrel from a 283 Chevy. Above 5000 RPM it ran great. Would NOT idle at 2000 RPM!

Both Carter and Zenith produced "universal" carbs in the 1930's with slotted throttle bodies. After WWII, both ceased this practice, and produced a wider range of "universals" with different internal venturii.

And for O.E. applications, many more (check out Panic's post two above this one) were produced.

Stromberg, to my knowledge, did not slot the throttle bodies. The link below, while it is for updraft carbs, not downdraft, may explain the "sizing" criteria better:

http://www.thecarburetorshop.com/Stromberg_SF_carburetors.htm

When choosing a carburetor (or anything else) don't discount the five (or 6, depending on language skills) "P"'s of Engineering.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop