There have been a couple of threads again suggesting that there is some misunderstanding of carburetor identification. Here are some links that may aid the novice in understanding the terminology, and better selecting non-original carburetors:
Carburetor identification:
Common carburetor types and actual identification criteria The above link lists a number of series of carburetor (not unique) and what to look for to find the unique carburetor identification.
Updraft Stromberg carburetors:
Listing of updraft Stromberg carburetors by series The above link lists common Stromberg updraft carburetors, years produced, and physical (not airflow) sizes.
Carburetor CFM:
CFM history This link describes different CFM ratings, and conversions from one rating to another.
Jon.