Duralast 433 "Economy" Brake Shoes?

Did you look at all the shoes? They're not all the same. There's a primary and secondary. I think the one with more material also goes to the back.
Also, thought there was a change made to the 7.25 rear end around 73 that changed the backing plates, but maybe this only applied to BBP 7.25 rears or maybe those with 10inch drums.