Chris & Hank;
I think Tim Adams made some very good points in his comment. I will say it this way......each build type has different points to consider.
If you are staying with the stock engine there are at least a few different Cherokee axles that may fit the bill depending on what you are trying to achieve.
I went with a Dana 35 out of a 2WD 2000 Grand Cherokee. Since I am staying with the old flathead I feel that the axle is plenty robust. Big things for me was the 12" disc's, a 3.55 final ratio and the 5x5 wheel pattern. This axle allowed me to keep a pretty stock appearance on my 3/4 ton while giving me the better brakes and higher ratio. This is huge as far as I am concerned as this truck will be my daily driver. Easy fit too. Swap the shock mounts and it was a perfect fit. All I had to do to get my original 15" rims to fit was a bit of light grinding on the calipers and add some 3/8" thick wheel spacers. I believe the rear gained about an inch in overall width.
This was the best option I could come up with for my build. Might not be the same for a guy with a 1/2 ton.....different wheel pattern? or the fellow that is stuffing a 440 into one of these trucks. You really have to look at each build carefully.
Hope this helps.
Jeff