There is limited info on IDing Rochester carbs because they ARE SIMPLY NOT WORTH DOING AN EXACT IDENTIFICATION !!! The chart on the website clearly shows many different carbs used the same castings by number.
With few exceptions (the 1949 and 1950 Olds, 1951 Cadillac, and 1955 Olds 2-barrels come to mind) here is the way you identify virtually all Rochester carburetors PRIOR to 1968 once the identification tag has been removed:
(1) Acquire Rochester assembly specifications for all carburetors pre-1968 (good luck, in 51 years I have acquired those from 1949 through 1959 ONLY)
(2) Totally disassemble the Rochester carburetor in question and measure ALL machined surfaces and pressed-in calibrations (idle air-bleed, idle bypass, idle restrictor, etc, etc, etc.).
(3) Compare all measurements sheet by sheet against all of the assembly specification sheets for the type carburetor in question until only one sheet is left.
(4) You have now identified the carburetor.
How much time has been spent ?
And you still have a Rochester B. Now you have to rebuild it.
In 1968, federal smog emissions required the identification number to be stamped on the carburetor.
For those truly in love with the Rochester B (I can understand this for an absolute numbers-matching show vehicle that is never driven), simply do a search on ebay for the one you need WITH an original tag. What is it going to cost ? The shipping charge may be higher than the value of the B.
For those that actually plan on driving their truck, better options exist !
Jon
