Well here's my take, sorry for being off the air for a little bit. WRT Torqueing bolts and stuff: I think one should not be trying to second guess the amount of friction you need to overcome to get to a torque reading, i.e., "dry threads". Entirely too variable. Some lubricant seems correct to me. As it is, there is Liquid wrench on there now, and so there is that. I am a BIG fan of Neversieze, but sounds like that might be going too far. Lets say I'll clean those threads up, they will be clean, not rusty, and I'll see how that all works out. What I think I want is to develop the correct pressure on those threads (which, as a simple machine, is really a wedge) so as to put the bolt in the correct amount of tension. Further, I think of this bolt in tension as a very very stiff spring, which means that it will stretch in proportion to the tensile load applied. And you want the working load on that bolt to NEVER come close to counteracting the tensile preload in the bolt and bring it to zero, which implies that there will develop a gap in the lash up. I do not have a problem with using 250-300 ft-lbs, and will report back about how that goes. Should be fine. I have no idea how much torque on that large fine thread amounts to how much tensile stress in that bolt, but I do know that the yield stress for that bolt is probably about 30,000 psi, and the section of that big bolt might be about a square inch, so that's ~30,000 lbs tension to get to the elastic limit. Even if only 1/2 in^2 root area, that's still 15,000 lb. The breaking stress would be higher. That shaft is probably pretty decent steel. Likewise the nut. The more likely failure mechanism here for overtightening would be due to shear stress in the thread. And thats a whole other technology -- read as "black art". Further note: I have learned that the replacement disk hubs come with a long spline or a short spline. Why this might be, I do not know, but I do know that my axle stub has a long spline and the damaged hub in the picture is a short spline. Which requires a spacer be applied so the castle nut has something to push against. And which also implies that the shaft has more bearing area in the spline than the hub can provide. Does not sound like a good thing. I will also inform that the replacement, due in next week, will have a matching long spline. Perhaps the short spline gave too little bearing surface for the spline, and the longer spline will fix that -??-
I also plan to renew the bearings, just because why not, It's all apart anyway, so a few more bolts and selected bad words to R&R those bearings. I think me nemesis might be that snap ring on the inner bearing. We will see.
As to precise torque readings, I'm kinda in the same camp as Stan and Pip: precision here is exactly what you need, for all the reasons provided above, when assembling an engine where the stretch of the bolt (remember, the bolt is a very stiff spring) must be just so to preserve close tolerances in parts that need close tolerances. This rear axle castle nut does not require these characteristics, so far as I can see.
Lastly, I do have a pneumatic impact wrench, which was handy to get that nut off, but I don't think I can use that device to "torque" the nut on.