If you do your reasearch, you will find ALOT of unsatisfied people that did rear disc conversions on these trucks. TCM makes a kit and another one. But both use car calipers which are not enough to stop there big trucks.
There is someone in the mix machining SD hubs to OBS pattern though to go with those brakes
I addressed part "A" here: Rear disc kit - opinion on it(long) - PowerStrokeNation : Ford Powerstroke Diesel ForumA: Because such people do not switch to a 97 SD or 450 Master to accommodate disc brakes
B: Using a SD axle is the only true way to go unless you figure a way to match big brakes on the existing housings.
C: You should not be able to lock your rear brakes up RWAL is what is ran in these trucks from 1987-1997 Which is Rear Wheel Anti-Lock. It works by pressure hold, pressure release and pressure hold again. Just like pumping the pedal only faster then you can do it lol. If you can lock them up you need to check your ABS unit located under the D side floor board on the frame OR you have your rears too tight. What I have done for most customers is install a load sense proportioning valve or use a manual proportioning valve. Manual install with the use of a brake pressure gauge to make it a 60/40 split for those who don't tow often or a 40/60 for those that do.