I spent a few more hours fussing with this, and this is what I discovered.
My All Nation instruction sheets show that the big u-shaped bracket is closest to the motor; with the "mounting foot" outside of it:
However, on this Varney example (which has a different motor), the "foot" is up against the motor, with the big bracket outside of it:
Once I figured that out, it all came together fairly easily. Note that there are (2) tapped holes in the "foot", so one wonders is there was a modification made at some point. Odd thing is that I now have an extra brass washer; where that came from is a mystery.
It is perfectly sized to fit on the worm shaft, but upon installing it, it was too tight and bound up the mechanism.
As it stands now; given the fact that it's missing several crucial pieces, it runs very well up on blocks. Am hoping that BTS can come through with those parts: (in the meantime, I am open to any suggestions and/or offers... 
 
Mark in Oregon
EDIT: By swapping the 2 brackets back to where they should be, we gained enough space on the worm shaft to put that washer back where it belongs...🙂
