While it impossible to totally identify a Rochester B carburetor from the casting numbers, we do have a listing of casting numbers which were used on some of the more common Chevrolet Rochester B carburetors. These castings were machined a variety of ways, and therefore castings (with different machining) will be used on different carburetors (some that are not even Chevrolet). In any event, perhaps this list will help:
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I do not have data to take the listing newer.
Jon.
