Your running Toyota axles, so your going to probably want to hit Pirate or a Toyota forum for brake info on a disk brake conversion.
For cutting brakes there are a couple ways to go. One is with a line lock for each tire, or just each rear. That way you can lock one rear tire up and spin around it. However, if you have a rear locker and not a selectable (arb, ect) then this isn't going to help much.
To upgrade your master cylinder I was looking around and found a post on a Canadian board that mentioned that both a 92 Civic Booster and Jeep Wagoneer booster will swap in. But the Wagoneer requires a swap to standard flares for your brake line. Might be a good read for you.
Link to Thread.