I'm pretty sure you can save it.
I took this, which had been out in the Alaskan weather for over a decade...
And turned it into this...
Without any particularly amazing effort. I won't lie, there was a lot of labor there, but 90% of the rust was easily killed with the common electrolysis method- even the big main "tree" casting, which I just had to make a temporary "tub" for with 2x12s and Visqueen.
The only thing that's been holding me up is a broken gear, which I don't have the tooling to make nor have I been able to find a replacement.
Take lots of digital photos of the teardown, especially of the smaller components- hold them so that the picture gives you an idea how they go back together. That was an invaluable help for me.
Derust, brush-polish the exposed parts, paint with a good alkyd enamel, replace any bearings or broken parts, and since it's almost certainly 3-phase, ditch the switch entirely and wire in a VFD.
And show us as you go.
Doc.