When you go to rear disc you will want to change that master cylinder.---trust me on this.
I switched my fox over to SN-95 disc all the way around and I didn't touch anything under the hood
the pedal felt fine and the car braked well. --never changed the booster or master cylinder.
Now a year later the back pads are gone and the fronts look good. Some how the old master cylinder
holds a very small amount of pressure on the shoes (must be a check ball some where) and that don't work out with disc. -- it never felt like a brake was dragging --so it must be a very small amount of
pressure--- But it will bite you in the butt sooner or latter.
This is not what I heard or read this is what I know -I did it