I just finished rebuilding a steering box for 1958 tr3. They are a little more difficult because in getting them out one has to take off the front apron because off the long column, but I needed to have a repair made in there anyway. I found a stock pullback tie that goes in the center of the apron at the bottom and then attaches back to the frame on that center bracket. I had broken mine off at the frame years ago. Evidently, Moss does not have a number for them (weird). Yes the steering box can leak from a number of spots. In addition, in the shim pack there is almost always one or two brass shims and the main shaft bushing is brass. I do not know about the brass sulfur problem because I never experienced it before. Anyway, I use the same stuff that I put in the rear axle; I think it is Castro oil 90-70. Yes I would say that it is about 50/50 dry or wet, I prefer the wet. Sometimes they leak out at the: brass nut and olive at the center end (where the wires come out), sometimes at the bottom seal where the pitman attaches, sometimes at multiply points in the shim back (if someone loosened the bolts) sometime the top cover (Don made a good point) and some times a combination. The point is they need fluid. If the fluid runs out and you do not want to do a bunch of work; you can use packing crease. Just fill it up with that and it will at least have some lube.
If you want to rebuild the steering box and do it proper, the units are like most things on a tr3, simple and beautiful. The hard part is getting the pitman arm off once you have removed the box. You need quality pullers, but it is just one bolt. Moreover, the project is one of those rebuilds that when you are done the guts are not too tight or not too looses. I use Indian Head gasket sealer on the shim pack and to top cover. I usually have the brass bushing pressed in and honed at a machine shop. However, the next bushing I am going to do myself; it does not look that difficult. I was just going drive the new one in and push the old one out at the same time then get a horn and do it myself. Once I used packing grease on the shims and that sealed. Most people are not familiar with that old trick, but for example, if you put a healthy bead of packing grease, on say a valve cover; it will seal and not leak and come off easy.
Good luck in advance Sp53