Carter W1 - 684S --
wrong - this is for 1949 Your YF could be a replacement carburetor (I think a YF might have been a "universal" replacement). Carbking will know for sure.
Correction added later:1946 carburetors Carter W1-616S (downdraft) - 3000, 4100, 4400 series
Carter W1-574S (downdraft) - 4502, 6000 series
Carter BB!-517S (updraft) - 5000 series
