Have -- knock on wood -- finished my power steering saga. After all sorts of leaks and problems (and some screwups on my part), I got my hands on a rebuilt 80 gearbox; fully disassembled and rebuilt the pump, along with a little extra gasket sealant; battled the pitman arm (and ended up needing a new drag link end); added an in-line magnetic filter; re-did some hoses; and recalibrated/centered the steering wheel. Drives like a new truck. Only wish I did it before a road trip to Nashville / Western NC. That was some interesting driving.
The 80 series gearbox is just about plug + play on the 60. I reused the 60 series pitman arm (different drag link bores, but same splines on the gear end), needed one stretch of longer return line hose and its slightly larger dimensions required some jiggling and BFH tapping. If anyone is tackling your steering assembly and need some help, lmk. I have made all the mistakes already.
I also have an extra 80 series pitman arm (not the 105 bore) if anyone might need one.