I was finally able to get both Wallstreets to boot into OSX yesterday. Long story short, the CPU in the machine that’s been working hard serving the website for the past year-or-so is displaying signs of heat damage, and freezes, every time, when one attempts to install OSX from CD.
So I installed from CD after swapping the CPU card for the new one from the more recently arrived machine.
More tinkering yet required, of course. Just making note of it.