Manual steering to power
You have lots of choices on which way you can go with this but it would all depend on your budget, you could probably do the change over for little or nothing if you used all junk yard parts. I would look for a low mileage car for the steering box with the same size sector shaft as your current car and get all the parts off it to do the swap.
You could also get a rebuilt box from Firm Feel or Lares , I have used both and had no issues. The Lares box is probably a couple of hundred dollars cheaper in the end and could ordered through a local parts store which will save you shipping a core to Firm Feel.
PST also sells the boxes and a lot of the parts to do the install and they give members here a discount so this may also be a good option for you if you want a Borgeson box with the faster ratio.
Bergman Autocraft will also supply you any of the parts you need to do the Borgeson conversion all the way to a complete set up that includes all the pulleys, brackets, hoses and even the fluid. This will be the most likely be the most costly ( $ 1500 if you get everything ) but it is all new and will be the best performing stock type steering currently available.
Pick your poison...