The rear brakes do less than 20% of the stopping on most vehicles, unless you're hauling maximum gross weight most of the time. Drums make good sense on the rear, with an upgrade to front discs being a much better idea. Look at the rear disc setup on most of the modern vehicles- - - -the piston size, disc diameter, and pad area is a lot less than the front. This is done mostly to prevent rear wheel lockup on a panic stop since weight transfer puts a lot of the braking force on the front.
Jerry
