These are a pair of 11 X 2 1/2 inch rear brake backing plates that are used on van, pick up truck, passenger car Dana 60, 9 3/4 axles, and 9 1/4, 8 3/4, and even the 8 1/4 inch axles.
I just pulled these off a late 70's...
Brake Backing Plates 11 X 2 1/2 Inch, Levers & Struts, Spring Hardware.