Simple project if you are good with vehicles. Ford Motorsport makes a kit. it includes, capliers, Bosch Rotors, and parking brake backing plate/caliper mount.
Essentially, you just remove the rear differential cover to remove the center pin from your spider gears.
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Remove your axle. Only do one side at a time.
Once the axle is removed, it should look like this.
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Remove the drum brake backing plate.
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Put the new backing plate on.
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Put rotor and caliper on.
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Do the same for the other side. Fill the differential.
You will need the brake hoses from a 1996 Explorer along with the banjo bolts and copper washers. You will need to make the steel line that goes from the left wheel to the right wheel. Use 2003 Trac rear parking brake cables.
Adjust the parking brake with a drum spoon and your parking brake is set properly.
Bleed your braking system and I recomend speed bleeders, they make your bleeding process simple.
Burnish your brakes in and you are finished.
<font color=red><B>EDIT:</B></font> Change your axle seals while everything is apart. Better safe then sorry!
Tom