Such a simple question, with such a difficult answer!

If you have the original tag, then the answer would be quite easy.

If the tag is missing, then:

Rochester type B carburetor - 164 different carbs, we make 36 different rebuilding kits
Rochester type BC carburetor - 56 different carbs, we make 25 different rebuilding kits.
Rochester type BV carburetor - 64 different carbs, we make 26 different rebuilding kits.

So, in summary, Rochester produced 284 DIFFERENT carburetors which are often referred to as Rochester B; for which we make 87 DIFFERENT rebuilding kits.

And with no offense meant to anyone, personal (and professional) opinion is that if the tag is missing, just replace the carb with either (A) a tagged original Rochester if you are a glutton for punishment, (B) a Carter, Stromberg, or Zenith replacement carburetor, or (C) a 15-year-old standing on the running board and pouring gasoline into the engine out of a leaky boot wink

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop