Eaton rear brake size question

[Dean]

I'm in the middle of doing a body off restoration on my 4th 71 K20 and I have a question about the rear brakes. This particular truck has smaller brake shoes (2" wide") and drums than any of my other trucks. All the other ones including my C20 has shoes around 2.75-3" wide. I knew there were differences like finned vs. smooth drums but I wasn't aware of the size difference. I am installing the bigger ones on this truck, but I was just curious. I had to switch the backing plates as well. I was wondering if someone swapped these in the past or was there two different sized rear brakes?

All of my trucks have the Corp/Eaton rear of course.