The adapter thing is a total scam. I've taken several power and manual steering columns apart over the years, and the internal shaft (sliding part) is THE SAME! Chrysler used "plastic rivets" to create just enough drag on the sliding part of the shaft to keep it from flopping around while being handeled on the assembly line. Those rivets don't penetrate the sliding shaft at all...they just poke through holes and rub against it.
If you take a P/S steering shaft, and pull the center all the way out, it would actually touch the steering box itself, and STILL have 100% engagement with outer, or driving part of the shaft.