What disc backing plates do I have

[gmc4x4can]

Im doing a drum to disc on my 70 k10 with the disc parts that the previous owner gave to me with the truck. Ive ran into a problem. The disc rubs on the backing plate at the top of the pic. Ive pointed to the stamped in hump which is near both caliper ends, I cut out these humps but now i find that the offset of the mount is different and i cant even get the inboard pad between the plate and disc. The bottom plate works fine, no hump and disc doesnt rub, pad and calipers fit fine. They are 1/2 discs. I would like to buy another like the bottom one, but need to know the year I guess as I didn't buy it. Thanks guys
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[abig84]

those look like regular ol gm 10 bolt backing plates (obviously) never noticed a difference before maybe some kinda change between years.

since no one replied i went out in my pile-o-parts to find some of these backing plates, i know i have them but no clue where they went.

but i did find these and they dont seem to have the hump





came off a 1977 8 lug dana 44. i always liked these better as they had a good solid heavy backing plate not the shet metal ones gm used later on. dont know how rare these are to find i just bought the entire axle for like 50 bucks last year for a project im working on

i wonder if you can just start googling different years followed by "10bolt backing plates" and see if any match the ones you want.