Power Steering Upgrade Questions

So I have a '75 Duster (slant 6, no power steering, no ac, 3 on the tree) and my original manual steering box gave out (worm gear shredded itself). This is my only car and my daily, as I'm 17 and this is my first car. I have a decent amount saved up and decided it's time to go power steering, since i eventually want to swap engine/trans and add A/C and such. I've been looking to get the Borgeson 800127 steering box. It looks like I'm going to need to cut the steering shaft since it's a factory manual steering car, and I'm not sure how to add the PS pump to an engine that runs only the fan and alternator on the fan belt.

If anyone knows about fitment from my steering column to the new box, have suggestions on boxes or pumps to use, know of any brackets to use, please help.