I made the upgrade on my 69z. I purchased a Power Steering set-up from a guy on eBay (cost me $404) and it had everything. And yes, it needed an appropriate Pitman arm. Here is a picture of the items in the set-up and all the parts were used.
The box was rebuilt, but the cover leaked as the gasket was pinched. A new gasket solved the problem. The other parts were clean, but needed some work to make them real nice.
If you want the name of the person... His name is Jim at 480-981-3096 or 602-751-0454. Here is a link to the set-up you may want:http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=290065803776
Note that I have the Close Ratio box, and it is a little too quick for me. I even purchased a shorter pitman arm to slow it down a bit, but I have not installed it since steering geometry may me affected (as I was told).
If anyone has a comment if I can put the shorter pitman arm on to make it less snappy, please let me know.
Oops... I see you have a BB, but you may want to inquire anyway as he may have the set-up you need.