One of the many issues we face when selling carburetor kits is the accepted myth "they are all the same" or "one fits all". And then I am the bad guy for not wishing to sell a kit if the customer does not have the original identification number.

Ulf is indeed correct that Rochester DID make a flat shaft pump for some of the model B carbs. In fact, they made more than one! They also made more than one with the round shaft. Several in fact. Just to prove the point, I grabbed three different (2 round shaft and one flat shaft) for the picture below.

http://www.thecarburetorshop.com/Rochester_B_pumps.jpg

There are also a number of DIFFERENT airhorn gaskets, and throttle body gaskets; which are NOT necessarily interchangeable.

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