I completed this conversion today - with a slight variation. My local yard didn't have an XJ in the right year range, so I started looking at Grand Cherokees to see if I could make something work. I found a (I think) a 1997 model Grand Cherokee and both CV joints on the shaft were visible in the engine bay. On later models the shaft extends through the firewall and the top CV joint is inside the cabin, so a little long for this application.
The 1997 GC shaft is the correct length, but the end doesn't fit the boxed end of the steering column. My solution was to grab the top end of a stock GM shaft, the version that fits inside of the steering column. I had to shorten the end with the bolt hole by about a half inch so the bolt hole would line up. I then cut off the other end, leaving 3 inches or so sticking out of the column.
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The shaft has a rounded profile on two sides, so I used a grinder to flatten the profile so it would fit into the Grand Cherokee shaft.
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A few pics of the final fit up.
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The advantage to using this shaft is that it isn't necessary to break the two sections apart to make it work. The shaft is long enough that no mods are needed.
Last month I replaced the rest of the steering gear - inner/outer tie rods, upper and lower ball joints, center link, pitman arm, idler arm, idler bracket, and a quick ratio redhead gear box. This final mod cleans up any loose feel in the steering.