'65 Dart window glass installation...HELP!

I've tried installing the window glass first, but then can't get the vent assembly to go far enough to the rear (because it hits the side glass) for it to the front opening.
Then I've tried installing the vent window assembly, but I cant get the regulator arm into the bracket on the window.
The FSM describes doing it either way, like there's nothing to it. Well, it's not working either way for me, and I've attempted both ways several times. Tried with the regulator loosely bolted up and with the regulator unbolted.

Any advice for a man defeated by a window glass?