Thinking completely outside of the box here. I have a '67 Corvette with power steering. There is nothing in the steering box itself that has anything to do with the power assist. After getting the pump mounted on the engine, everything else is external and should bolt on. All parts are readily available and priced reasonably.
Here's what it looks like :
I bought the unit on ebay. Just came out of a 10 day stay in the hospital. The seller says that the unit came out of a running car and is totally functionable. They are changing the car to a resto-mod. I need to put this on my '53 ford.