I don't doubt that a shiny new box is the best thing since sliced bread, but it isn't in my 80's future at these prices, unless completely unavoidable.
Yes, the weak Yen helps us USD buyers, but ~$1200 is a whole lot of money for me to spend on something that just has a little seal leak. Not that ~$1200 in and of itself is a catastrophic amount, but it's more than I want to spend on this right now. I'm Yankee/Scots frugal.
I'm psyched for people that are able to get a new box with the upgraded shaft and arm. It sounds like a great time to buy due to exchange rates, an opportunity to get one while they are still available, and also gain the benefit of a new, perfect part to improve function.
For my part, I'm buying a used steering box from a 'mud member and a rebuild kit (Toyota parts from Japan, benefitting from the exchange rate). I'll weld in the Delta plates, and install the used box, then reseal my original as a spare. If stars align, and I find a super deal, maybe I'll even rebuild with a 105 shaft and arm. Hopefully this works out and I'm not being penny wise, pound foolish.
Again, thank you for the information, perspectives, guidance, and terrific discussion.