Thank you all for help with my parking brake. I wish I had started this in a different thread, but can finish it here. There was no upper shoe adjustment - only the lower one with the large spring. I discovered that the driveline upper and lower shoes could be centered after tightening the lower nut either by use or by tapping the tightening mechanism with a hammer. And yes, there is a cable length adjustment on the handle in the cab, as described. It was just frozen like the cables and needed a good dose of penetrating oil and elbow grease to get it working. Now I just need to figure out the best balance between tight to hold the truck in place vs. loose to let it run.
I am also trying to attach a picture here in case anyone is interested in seeing what this truck looks like. So far, problems with the truck have been superficial (not internal to engine or other driveline or dump bed mechanisms). This is good since I am, so far, a superficial mechanic.
1966 GMC 5500 on return from VIN check
