I recently installed ZJ rear disc brakes on my 2001 XJ.
You can get the missing parking brake hardware at an auto parts store except for the parking brake levers and the equalizer bars.
I suggest getting a pair of parking brake levers off a XJ. Cut the ends off and weld them to the ZJ levers.
Doing this enabled me to use the stock XJ cables, after moving the parking brake bracket rearward. See parking brake relocation at
http://www.madxj.com/
The ZJ backing plates are thicker than the XJ’s. The studs, that attach the backing plates to the axle housing, are almost too short.
If you get a chance to bag a set off a ZJ, do it. To get them out, thread a nut partway on a stud, to protect the threads, and give it a good smack with a BFH.
You also may want to get a ZJ proportioning valve or just the guts (cap, spring, plunger and rubber cup)
http://www.go.jeep-xj.info/HowtoZJvalve.htm
The disc brake rotor flange is thicker than the XJ drum and the wheel studs are too short for use with alloy wheels.
I replaced the wheel studs, on the 8.25 axles, with longer studs from a ZJ.
Check the axle bearings and change the oil seals.
I also exchanged the calipers for rebuilt ones, along with fresh pads and hardware. I assume you are buying new rotors, since they are not shown in the photo.
Hope this helps.