Smart money for a 3" XJ rear lift
The YJ is a drivers side drop. The front from an 80+ Grand Wagoneer would work with some new frame brackets, the rear in those is an AMC 20 with one piece shafts. The Axles from a first generation Bronco can be swapped in without messing with the frame, but they require alot of prep work, they are Ford9"/D44. Fullsize Ford stuff if you want to go heavy duty. Or you could break out a large jar of vaseline and call one of the aftermarket/custom builders and get exactly what you want.
If you just wanted to concentrate on the rear and keep the D30 front, you can use a Ford 8.8" or an XJ/MJ D44 without any major hassle.