Jeep Repair: 89 yj, rough country lift, rear driveshaft

Question
89yj/3"rough country lift/auto trans/will a slip joint iliminater be needed?Also if the front sprins had degree shims should they be replaced with the new lift?

Answer
My opinion, lift kits are a waste of money. A spring over is the only way to raise a Jeep without screwing with the original engineering of the vehicle.  But since it's done, you will probably need a transfer case lowering kit that will bring your driveline angles into better alignment.  You might have to shim the front and rear differentials to achieve this also. Given the very short rear driveshaft, you will fight vibration from here on out.  Have someone with an angle meter tell you where you are and where you should be.  Most four wheel drive and driveline shops have them.
In addition, you should install a lowered pitman arm as that is now operating at angles it was not intended to.In addition, your brake lines are now at their limit and need replaced with longer ones.