Here's something I PMed firemedicsafd about the XJ shaft and extending it.
firemedicsafd said:
Flat part of steering box to bolt at the base of the column is 23" My column is 88' my steering box is 2wd unknown year.
As long as the steering box still accepted your stock steering shaft, it will work. The length is pretty long but I think the longer shaft should work. The problem with having to extend them is the lower plastic bushing that holds the two halves together tightly. If it comes out of the bottom when extending the two halves, you will end up with poor "interference" fit and a sloppy feel. If this happens, you will want to run a nut & set screw to take up the slack. Check out this post of mine.
http://coloradok5.com/forums/showpost.php?p=2754072&postcount=57
The middle picture (in that ^^^ post) shows the plastic bushings or spacers. The longer XJ shaft is ONLY longer AFTER the first spacer. So both shafts (short or long) have the first spacer in the same location. You can see the difference in my for sale thread.
Soooooo if you extend both shafts, this first spacer will be visible at the same length. The longer XJ shaft will still have 1" more shaft inside the other. So, if both spacers are still inside you'll be fine. But if the bottom one comes out, you should run at least one nut&set screw at the bottom to take up any slop.
Here is a picture of mine.
You can see the nut&screw idea better. I only did this as an experiment. It's also easier to get on and off since I can collapse the shaft. It was not necessary as the shaft is actually inside the other MORE than when it was on the Jeep. I have roughly 4,000 very hard miles on this, though half of those are with hydro assist.