I got some rebuild parts today, and could not resist putting the reg together just to see what would happen. Sure enough, it holds IP, and breathes fine on land. I'm waiting on some more parts (spring block, new HP seat, new diaphragm, etc) and the yoke is still kind of iffy, but it works! It's a little disconcerting to see the reg visibly move on the yoke when pressurized, but amazingly it does not leak at the tank/reg connection.
One interesting thing was that the spring inside the nozzle that I took out and the one in the kit were very different. The one in the kit was much stiffer and a little shorter. Since the spring block was also gone, I suspect someone may have rebuilt the reg with some "make-do" parts.
I'm really looking forward to finishing up and testing it out. It won't see water until the yoke, LP diaphragm, HP seat, and filter are replaced.
Regarding adjusting the 2nd stage, I have lots of questions but I'll wait until I get the new diaphragm. One quick one, anybody tried blue loctite for the nut on the LP poppet? Or maybe a drop of silicone? Something to keep it from moving. The manual says to center punch but I'm not too nuts about that one.