Good topic and questions. I don't mind taking a look at adds on Ebay and other sources for folks who are buying expensive carburetors to verify that they are real.
At this time most of them are fakes/restamps, so don't drop the hammer on one unless you have someone verify that it is the real deal.
There is also the "bait and switch" thing, where the seller shows pics of a real one, then sends a fake after the purchase is complete.
We get a LOT of restamped Pontiac Ram Air carburetors sent to the shop, and I have to tell the seller that they have just spent a lot of money on a carb that isn't the real thing.
There are a lot of indicators that a valuable carburetor isn't real. First look at the price they are asking, most are WAY under what the market will bring on one. Second, if the listing is running and no one is buying it, and the price is pretty low, rest assured it's most likely a fake.
Something else to mention here is that there are a lot of Service Replacement Ram Air carburetors out there, most were part numbers 7028276, 7029270, and 7040270. They will have Julian Dates much later than the model year run in almost all cases, and they will NOT have a Plant Code after the number.
The did NOT make Service Replacement manual transmission units, so a BIG flag should go up if you see a manual transmission Ram Air carb for sale with a later build date on it.
Carter didn't make any either, so stay far away from a Carter casting stamped with a Ram Air part number.
If you are looking at a carb for sale, and want me to take a look at it, send an email message to the shop and we'll respond so you can send us some pictures or a link to the add.......Cliff