Right Rear Drum Brake issue has everyone stumped

[Bacca]

I have had three different shops work on by right rear brake issue. 1st shop was a mistake on my part. 2nd & 3rd shops both ASE certified and well established in the neighborhood. I have a 1982 SWB. It came with a 4.1 automatic and disc frt. & drum rear. Every part that i could get has been replaced TWICE. OE when available and the best A/market I could find for all the rest. Drums, Shoes, Hardware, Wheel Cylinders have been replaced except the backing plate & the rear axle seals. E-Brake completely removed. Tried at least four A/market drums none worked. All bottomed out on the backing plate causing a bind. Ended up turning the original (I think it's original) drum and running it. Now the wheel gets pretty hot when driving. Every brake part Frt/Rear has been replaced including the Master/Booster. All steel lines are original and have good flow for bleeding. Near as I tell this truck never had a proportioning valve. I can't work on my truck anymore due to an arm injury but both shops allowed me to observe the repairs and their honest attempt at fixing it. I have countless drum brake repairs myself and I'm the first guy to say this "shouldn't be that hard" but here I am. Thanks in advance