Re: 2 Speeders from the 211/135 T-case. Its been a long time now, but I did all that, you have been discussing here. I used/installed a WW2 T-case, and blew it in a relatively difficult pull.
Trying to remember... there are several problems that I could not/or didn't solve. One is, that after you convert it to two speeds, the way I did it, is that you don't have a neutral, but just the hi/lo, so its a problem to use a winch. Another issue is the front wheel drive. It is full time w/spragues. The original tranny automatically shifted that for you, when you went from forward to reverse. I put a shifter lever in there, using another lever that came out of it. You just have to manually do the shifting of the 2nd lever. The front axle drive, is a slightly different ratio then the rears, so the spragues let it slip a little, till the rears go faster, then the front starts pulling.
To conver the T-case to two speeds, I think it is the big gear showing under the top shaft in your picture, that you have to make solid. As is, it is on a splined shaft. Then there is a large bearing insert around th splined hub, and an outer ring gear. I took that gear out, removed the bearing and turned a solid blank of metal, bored appropriately to be heat shrunk onto the splined hub, with an outter radius allowing the outside ring gear to be heated and shrunk onto it. Anyway, just look in there and find the big gear, with the bearing in the middle, and you have the right one.
If you take that T-caes to a heavy truck shop, those gear heads will figure it out, and maybe get you a neutral too. If you don't have a winch, its not much of a problem. I had one, but you just have to be in some gear too, but that leaves something else to work on later!
Later The 211 is a neat truck