I think you are on the right track because the rear drums are 1 3/4". I looked at that earlier and the references I found show that B-body drum is a 2.83" hub diameter. I have a feeling the brake drum he has is some that Moser bought and punched as needed for their application.
Trudyduster said earlier that Moser could make what ever brake drums he needed so I would contact them and see if they can do what the op needs.
The 8 3/4 we was working on yesterday was a Moser set up and they used a Ford drum.
