I couldn't find a number on the drum. I measured the inside of it though, and it was 11". I don't know what rear end I have but it's got 10 bolts if that makes a difference. I'm pretty sure it's small bolt pattern (4.5" x 5 sound right?).
10 bolts on the back cover is an 8 1/4" and to have 11" drums it has to be big bolt pattern. Big bolt pattern is 5 lugs with a 4.5" pattern. My advise is to take your drums and old shoes to a local parts store that can actually do something besides punch computer keys and see what they can do for you. NAPA might be your best choice.