There are three ways of getting disc brakes on your 3/4 ton.
This guy figured out a way to modify the existing hubs. It may be easier to swap the 3/4 ton straight axle for a halfton, then use one of the many disc conversion kits. The third way it to go IFS, which makes more sense if you're planning to do rear discs (which means a new rear axle). Personally, I would do front discs only, it will still give you much better braking and you won't have to re-invent the parking brake linkage.
