there are p/s boxes that fit in the same location as the original manual box so that the original steering geometry will stay the same and no bump steer that is common with other steering set ups. they are not a solid connection from the column like the original gear boxes were. meaning, the input shaft from the box is very long and has the steering wheel on the other end, no disconnect between the two. to install the p/s box the original colunm needs to be cut off, a bearing installed in the outer tube at the lower end and then the shaft gets a flat spot ground into it to accept a rag joint or u joint. I'm not sure how much room there is left for the column shifter box after that. there is a how to on google that shows the column shortening. there are new boxes sold as well as kits with new boxes and the parts needed. some guys have used a toyota truck steering box also but by now they are getting harder to find that are not already worn out or over priced.
check this link to see a system installed
https://www.motortrend.com/how-to/po...traight-axles/
and a thread on this forum talking about the toyota boxes
https://67-72chevytrucks.com/vboard/...d.php?t=593492
a google search will show lots of options