rear brakes get too hot

let me try to give more info. I have not used parking brake on either car , parking brake not causing excessive drag. Front and rear brake hoses and wheel cylinders have been replaced on both cars in last few years. 69 cuda has rebuilt calipers and new replacement master cyl. and booster. My main concern is with the 69 the 67 I only drive to work a couple times a week ( future project ). Gear lube in rear full 10 inch drums all parts store replacement shoes wheel cyls. and hoses no mix/matched parts or high performance parts. I do have " green axle bearings " in the 69 plan on changing back to tapered bearings. Don't want to start a bearing debate but had a green bearing fail possibly due to excessive heat from brakes. What is the correct wheel cyl size for the rear and can anyone suggest a slightly smaller dia. cyl. size if this might correct problem ?