Original 11in drums on an A-body?

A few years back, this random guy gave me a complete 8.25 A-body diff for my dart. He said H pulled it from a 73 Dart. So when my 7.25 finally took a crap on me, I decided it was time to rebuild the 8.25. When everything on the inside of the diff was done, I turned to the brakes. The drums that came off (rotted off rather) were 11x2in. So when I went to purchase new ones, I was told that that size does not exist for A-bodies. After about two weeks I had figured that a 74 B-body had the same setup. What I want to know is was this a factory mishap? The diff was complete and seemed to be original when I got it.