Well, it's a very rare carb, so I didn't want to announce this one to the world, but I just got this on epay....
7028271 Quadrajet

The seller has good feedback and his ID goes back to '05, and the photos looked legit as far as I could tell, but I am no expert. The carb looks just like my 7028276, and the stamp seems to have the correct font, position, and spacing. It does not look like the surface under the stamp was milled, but the detail of the photo is not great.

Any opinions are welcome, as are snarks at me for paying such an outrageous amount for a carb that still needs to be restored. (I'll be checking back here from my cot in the garage, which I will likely be sleeping on tonight. )