Rear drum brake backing plate question.

[bopperd]

I am restoring an old W-150 4x4 4-speed pickup with a slant six in it. The rear axle is a Mopar 9.25" with 10" drum brakes. The backing plates have turned into swiss cheeze and I'm having a hard time finding replacements. I have found two sources for plates that fit an 8.75" rear axle in a Duster or Dart. But when I look at the pictures they appear identical to what I have. My question is whether the mounting flanges on the two rear ends are the same. Anybody out there with experience in this?

Thanks in advance,
Dave