I to have seen lots of carb numbers changed over the years as I work for a Delco distributor here in canada. We used to rebuild carbs as a specialty when we had a service shop in operation. Over the years we have seen plenty of swap meet carbs re-assembled with new fresh stampings. We used a 9C Parts and service manual to let the customer know if the insides matched the so called castings.This manual did not show us date stamps but gave us a parts breakdown of all the pieces matching the castings(jets,rods,chokes etc.)Im sure now with e bay the temptation to make some money is greater as your customer is unlikely to be a local guy.
If anyone is interested I have a 9c parts and service manual that covers Rochester Carbs 55-71 canada, and 51-71 Usa. My car is a 72 so I have little use for it.This manual also has all the service specs for setups after rebuilding.
If anyone is interested post here or e mail me direct.
[email protected]
Thanks