I've been working on my 1973 Duster, a base /6 car. It has the power front disc brakes.
We were putting a new stainless steel fuel line in the car, and to make it easier, I took off the right rear wheel. While the wheel was off, I pulled off the brake drum to see how the brakes were. I was surprised to see it had 10" by 2-1/2" drums and shoes. I measured them, and yes the shoes' friction surface is a full 2-1/2" wide, as are the wear surfaces in the brake drum.
I was expecting to see 10" by 1-3/4" like on an 8-3/4" axle (mine has the big bolt pattern 7-1/4" axle, 2.76 open gears), or 10" X 2" at best.
Would the car have been built this way with the power discs up front, or could someone have changed them?
There's one build sheet in the car under the rear seat, but it's pretty brittle, I'll have to get 2 people to hold up the seat springs while I slide the sheet out. I'll have to see the codes for the brakes, if that part is still there.