Has anyone actually broken a steering box?

fatigue is normally a factor. I've not broken an A body one, but I have broken one in a 78 powerwagon. Also keep in mind, reman'ed by who or what? Reman'd means they are re-using 40 plus year old parts and just replacing the wear items such as gasket, bearings, etc.

That said, I'd go get one of those smaller, light Borgeson power steering boxes

Good point about the old parts. There are new OE looking boxes being sold now though.

And, the the borgeson boxes are smaller and lighter than OE power steering boxes. They're not smaller or lighter than the OE manual steering boxes. Here are some weights. I weighed the OE manual, power, and flaming river boxes. The Borgeson number is using math and Peter Bergman's info from his website.

OE manual steering box:..........................12.4 lbs
OE power steering box, large sector:......... 37.5 lbs
Flaming river 16:1 manual box:……………………17.8 lbs
Borgeson power steering box......................22.5 lbs (per Peter Bergman, 15lbs lighter than OE power box)