I decided that since I needed to adapt the alternator I had, and I wanted to go to a Premiere Power Welder eventually anyway, I bit the bullet and got the alternator/regulator package for now. I'll add the control box for the welder next year when budget allows.
I got the Ford small case PP160 alternator. The bolt fit but that mount extended farther than the factory alternator. Some careful measuring and a couple minutes with the Dremel and it fits perfectly.
But the stock replacement belts were just a hair short so I need to run by the store this evening and get "one longer" belts.
I'm in the process of replacing the split loom tubing on the wiring harness and doing things like getting rid of the choke heater circuit (as I no longer have a choke). So wiring this new alternator/regulator in also makes more sense now than redoing stock and then going back to redo it later.