nytrdr24
+1y
if you wanted to swap to a 4wd 90-97 yota rear end (i believe that is the correct years, would have to double check tho, they are the same width from wms to wms, and you get a couple different gearing options), you can get a disc conversion for it from downey off road.....
also, i've heard of using late model chevy rotors, and calipers off of a montecarlo.....someone else suggested using a pathy rearend that already came w/ disc.....other than that, if you plan on going to a 5-lug setup, you could do what i've started on, 84-85 rx-7 gsl-se rearend, they are limited slip, 4.07:1 gear ratio, and come with disc already which is nice, but you'll have to cut off all of the existing bracketry (as those rx's were a link type w/ coil springs in the rear), and weld some new on bracketry, also it is a 4 x 4.5" lug pattern, so you will have to get the disc & axles redrilled (won't work for 6-lug application as the disc are too small in the mounting surface area) you can reuse the trucks e-brake cable on these calipers, but will need to have the cable shortened a little, and a button crimped on the end.
this topic has popped up every now & then, and think limequat had done some research into the pathy rear, and maybe another as a source for a rear disc setup......