2 different 10x1 3/4, 8 3/4 backing plates?

Dana this is the first I've had someone point out difference in nom 1.75 x 10 backing plates.
I switched my '67 over to '69 hardware and shoes. AFAIK that (the adjuster hardware) is the only thing that needs to be consistant. You can even get away with the 331 shoe frame on an earlier system, although I've had part store guys say the 'Ford' shoe, 151?, is a better match.


Now I'm the one who doesn't remember. But I guess there was a change in the brake cylinders, and the backing plate with tabs maybe related or is just a way to rpevent the pistons from coming out. Someone here will know.