11 x 2 Brakes?

So, I installed an 8.25 in my Dart....it has an unknown pedigree. When I put in the carrier, I had to use early style bearings, so I figured it to be an early (mid 75 back) rear. What year did the BBP 8.25 start showing up in A bodies? What else could they be in that would fit an a-body?

The reason for the query is my unfortunate experience buying brake parts....it had 11" drums, so I assumed 11 x 2.5, and ordered accordingly. BUT when I pulled it down, they are 11 x 2s. I tried putting the shoes on, and they fit but I could not install the top return springs....what could the backing plates be from? And when did 11 x 2s show up (if ever) on these cars?

sb