8 3/4 backing plates onto a small bolt with upgraded big bolt shafts

One other thing. In regards to the backing plates and the adjuster cable/screw.
I've discovered that the adjuster mechanism that Chrysler used changed for the 1970+ model years or so it seems. So my question is, was there any difference between the backing plates for an 11x2.5 inch setup of say 1968 compared to the 11x2.5 inch plates of say 1971? As I am considering using the 1970+ adjuster overload spring cable setup but I am not positive which year of vehicle my plates came from. All I am sure of is they are 11x2.5.
PS I exchanged my 11x3inch plates for 11x2.5.drum_brake_system.jpg download (2).jpg