The one thing I had always wanted to replace on my XJ were the rear brakes. I could never keep them adjusted, they never had enough stopping power or they would lock up in the rain. So I went about looking for a set of discs that would work on the back of my XJ. I checked Explorer's first and actually tried to bolt the backing plates up, I looked into S-10 blazers with rear discs, Mustangs, Camaro etc.
I really wanted the internal drum parking brake and I wanted it to appear factory. I was really leaning towards the TSM or SS brakes YJ kit simply because even my cost (worked for dealer) for the brake parts was going to run me $500+. I came across a wrecked 95 ZJ that had a bent rear axle housing, the owner said I could have the brake assemblies for $100. So I jumped off the toilet and headed out with my tools. This worked out for the best because I even got the parking brake hardware and short soft brake lines.
There is not much detail to this swap onto a Chrysler 8.25 or a D35c, I will go over the basics and provide some photos to illustrate the changes I did make. *NEW INFO* when upgrading to discs on a non c-clip D35 or D44 Early 90's and up Crown Vic with disc brakes caliper brackets have the same mounting pattern.
First the axle shafts will need to be removed, drain the rear diff and removed the cover. Then removed the cross shaft retainer bolt and slide the cross shaft out. push the axles towards the center to let the c-clips drop out then pull the shafts straight out.
Remove all the brake hardware including backing plates and disconnect the hard brake lines from the wheel cylinders.
to mount the caliper backing plates on the 8.25 you will need to clearance the inside approximately 1/32" I used a die grinder with a carbide tip, ground a bit, tested then ground some more until they fit snugly.
(click on pictures to enlarge)
Once these are bolted in place of the drum backing plates you can replace the rear axle shafts (in some cases you may need longer bolts to retain these plates to the axle assembly).
The brake hard line will need to be rerouted to the caliper soft line, I flipped the soft brake line on the calipers to go the opposite direction, then welded a small plate to the axle tube and tapped holes to mount the factory soft brake line:
Here are some pics of the brake line routing
I modified the parking brake lever to accept the factory XJ parking brake cables, by removing the last bit of the drum parking brake arm and welding it to the ZJ park brake arm:
You may also need longer wheel studs, again depending on application.
I have made no changes to the master cylinder or proportioning valve, at some point I plan on upgrading the master cylinder, vacuum booster or both. I have had no pressing need to simply because the Jeep stops better than it did stock and it is on 35" tires now. I would put this at the top of my list for modifications.