so im looking to get disc brakes in the rear. so I heard I can use a ford 8.8 from an explorer, but I am not sure about the drive shaft bolting up to the diff ? would I need a customized yoke or something?
Most likely. The issue I ran into is that my factory driveshaft didn't have serviceable u-joints that allowed for a simple yoke change (required) which left me in a position to have some fabrication done to it, or just have a new one made. I opted to have a billet driveshaft made. Cost me $600 bucks for what I had made, but was worth it for the piece of mind.
...and if you're putting that 8.8 in your 87, you will need to shorten it about 2" if memory serves. 89-95 pickups are within .5" Good part is that it'll bolt up like its supposed to be there. You will need to "adjust" your gas tank a little with a hammer too for fitment.