So, eventually, I could that Call A.P.P.L.E has an old software list that contains a disk image of the "Basic Connectivity Set." Which contains a bunch of System 7 tools and a single System 6 INIT.

But, ClarisWorks still says the toolbox isn't installed, even with that INIT.

Then. I found out that Zterm doesn't rely on it.

So, that gets me where I was going.