Here’s a pic of the backing plate from the front, and one sitting in the drum. The outside circumference of the backing plate is 11” on the nose, and yes I’ll sell you these, with or without the drums.
Just for information, parts purchase, and re-assembly purposes, that upper washer needs to be flipped 180 so the ears are at the top. Also, the upper photo is the passenger side (RH), and the bottom photo is a driver's side (LH) off a '70-72 model.