to the o/p if you can.. find a 78-81 t/a with 4wdb get the e brake cables, the master and proportioning valve, the clappers and maybe the rotors(if they look turnable), the backing plate/clapper mount
the clappers are for rebuild or cores.. that be the cheapest... also same year caddy's(reardrive)
you can still get everything new.. rotors/clappers at your local parts house. allong with the master...
the p/p valve and backingplate/clapper mount you'll have to get from ames performance/yearone or other sources.. the e brake cables.. you can get from local jobbers or resto houses
fyi some 81 camaros had the ws6 rear disc also.. not many but some