Brake drums for the 3/4 ton and 1 ton AD axles are pretty scarce and expensive when they can be found. I've seen some pretty nice conversions to disc brakes, front and rear, that allow you to upgrade the braking and use newer, less expensive replacement parts. If he's using the truck commercially, even with moderate loads, an upgrade would be a good idea, especially if the truck is ever involved in an accident.
Jerry
