rear brakes get too hot

^^^ My thought too.... gear oil topped up in the rear axle? Any bumping of the wheels at low speed?

- Also, is this a changed out rear axle? What size drums are back there? Need to know both diameter and shoe width.
- Need to know front pad/shoe and rear shoe types; pad/shoe materials being non-standard on either end could make the coefficient of friction high on the rears or low on the front, that will make the rears do more braking and hotter.
- Need to check the diameter of the pistons in the rear wheel cylinders and the front wheel cylinders for the all drum car. The fronts being too small or the rears too big will do this.
- Also see if the fronts are actually working properly and are completely bled of air.

Yeah, lots of things to check that can be doing this.