Comparing Borgeson's power steering box to the mopar OEM box

Your steering shaft has to be cut. It is way, way, way too long. There is no adapter that will make that unnecessary! The adapter/u-joint/coupling is not the reason for cutting the shaft. The power steering box is longer. I did my Borgeson conversion many years ago and I went from manual to power steering, had to cut mine, but I can't recall the dimension. Isn't it in the instructions? Or, call them, I bet they know the exact dimension. Also, I had none of the problems you mention with the mounting holes. (I would not be surprised if their QC suffered when they moved down south, leaving CT for the cheaper labor.) Good luck!