When you remove the old steering box look at the frame for cracks. I recomend getting a steering box brace from ORD while you are doing this. You can also get an xj steering shaft to replace yours with.
You dont need to to all that with the xj arm, you can adjust the box with the bolt on top. That is what seems like more of a mod you would want with a body lift.
Also be aware that the PS lines changed the type of fittings they used through the years. I believe there is a year break along the late 70's or like 80'-81'. They went from like a break line style to an O-ring style. Just be sure to get one close as possible to your year and you should be good. You can also call NAPA and check the years ranges against PN#'s to find out the year break.
I don't remember the years for sure (95 or so I think) but their is some difference.Some of them have alum ends and the one you need will have reg metal ends with small u-joints.