rear drum brakes issue

I bet it's the shoes. I see a lot of listings for 10 x 2 rear brakes these days, which I don't think really exist — people just don't know how to measure them. Factory A-body 8-3/4 rear drums were 10 x 1-3/4, and that dimension is the width of the shoe, not the depth of the drum. People get confused and measure the inside depth of the drum, which is closer to 2 inches, and wind up using front brake shoes. The shoe needs to be significantly narrower than the drum.