I did this a few weeks ago on my 1979 R65. My advice is that having got this far you remove the top nut, separate the yokes, and clean out all the (likely disgusting and solid) old grease that you will find. You can then repack the bearings with a suitable grease (not wheel bearing grease, which won't warm up properly) and tighten down.
I followed the Clymer advice that you have found and after torquing down the top nut it was too tight. It took a few goes backing it off, backing the knurled not off a little, retorquing etc. until it felt right.
Note that the screwing down really tight of the knurled nut, then backing it off again, is especially important if you have regreased the bearings as you need to preload them before backing off to running torque. And I suspect that is what Clymer is really trying to say.