Got the Eaton 2-speed shift motor unit going back and forth.  Contactors ended up being too fragged to deal with so I temporarily wired a momentary pushbutton switch alongside the plunger switch on the gearshift lever.
Select Hi-Low then press button to momentarily energize circuit.  Simple and quick work around...

Bolted it up on the rear end and took it for a test drive - success!  The rear end shifts.

I've found replacement contactor sets on eBay, pretty cheap too.  I'll order parts and do it right soon enough.

Now to do a fluids list and budget, and deal with the front end.
I've already looked at the axle, springs, and kingpins.  Looks pretty tight, might just be tires and alignment...