Without a tag, there's no way to identify the application of individual Rochester B's. Is the engine in your 40 an original, or has it been replaced with a more modern one? The OEM carburetor on that truck would most likely be a Carter, since I believe all the Rochester 1 barrel carbs were post WW II production.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!