They might have a factory service manual at your nearby library. This would have an exploded view of the braking system.
Also, perhaps a better idea for your brakes would be to go with slotted and drilled Brembo rotors on the front of your vehicle. The front brakes do the majority of the work when stopping a vehicle. Upgrading the poor quality factory rotors will probably yield better results than switching the rear drum brakes to disc. This type of upgrade will be way cheaper as well.
1993 ZJ Limited 5.2 - no mods - Red with Gold (what were they thinking) trim.