Well here is the best answer we found based on the kits you can get at RSTGarage.com for the Jeep Cherokee XJ and the Jeep Grand Cherokee ZJ.
They have two sizes, the 1 inch kit is for lifts up to 3 inches. And the 1.5 inch kit is for lifts over 3 inches and they both install the same way.
INSTRUCTIONS – Read complete instructions before beginning installation, the following special tools are recommended: Coil spring compressor, floor jack, jack stands, and hand tools.
1. Park the vehicle on a flat level surface and block the front and rear tires. Place the transmission in neutral.
2. Loosen all of the engine mount bolts ½ turn.
3. Support the transfer case cross member with a transmission floor jack. Remove the 2 bolts, 2 nuts and 2 studs from each side of the cross member.
4. Slowly lower the cross member 1 1/8 inches to allow enough room to install the new tube or bar spacers.
5. Place the spacers supplied in this kit between the frame and cross member so that the edge of the spacers are nearly flush with the ends of the cross member and be sure that all the mounting holes are lined up.
6. Slowly raise the jack up to firmly hold the spacers in place. Using the new bolts supplied with this kit place a lock washer (if supplied) on the bolt first then the flat washer second. With everything in position place a drop of thread lock (not supplied) on the threads of each bolt in the kit. Insert the new bolts and torque to 33 foot lbs. Remove the transmission jack and set aside.
7. Re-torque the engine mount bolts loosened in step 4. The engines mount to block bolts torque to 45 foot lbs. The engines mount to frame bolts torque to 30 foot lbs. The through bolts torque to 48 foot lbs.
I am sure there are a lot of great tips you can share on how to install these so please leave a comment below.