I went to a HPD30 for a few reasons, one was price, I got a good deal, the main reason is that you gain a lot of strength having the pinion at the top of the ring gear, and you also get more ground clearance for your front drive shaft, mine was hitting constantly.
Ball joints are not expensive, and I used the Currie Johnny Joint mounts, you do have to get the reverse cut ring & pinion, just order it for the XJ and your good. When I did the front axle build, gears, ball joints and unit bearings. It's nice to have the piece of mind knowing it's all new and in good condition.
And of course, you get a nice axle to show off -
When I got the axle it looked awful -
A lot of cleaning and work later -