"Don't be so hard on yourself, it sounds like you've got busy-guy problems, not "effing stupid moron" ones. It's so easy to miss little details when you've got a lot going on, especially in multiple locations. At least you figured it out on the bench and not on the trail!
Two days back in my own garage really helped....I found it difficult to work in someone else's space (and tools), and getting to work on it once a week instead of everyday really caused me start-stop problems with trying to figure out where I left off, what was next etc....a lot of wasted time regrouping and probably led to some mistakes that I had to redo. Without a doubt, the sm465 is a much more tedious transmission rebuild than the T14 I did previously, or the D18 transfer case...in some ways, even the locker install with setting R&P backlash etc seemed to go smoother (albeit I wasn't setting up from scratch so pinon depth wasn't as bad as it could have been)....If I ever get this 58 project done, I have a 4:1 T18 4speed to go into the cj5 - from what I gather, it'll be between the T14 and sm465 in terms of rebuild difficulty, but I think it will have a mainshaft replacement as well - so its not trivial. By that time, I might be so sick of old jeeps that I buy something new, pay for shop labor to install a kit and just drive it.