Not sure if this is the right way, however it worked for my '40
Laid out glass on 3/4" plywood, traced perimeter. Banged in nails around the perimeter, and laid rubber gasket material around nails to determine correct length. Glued ends together.
Put a little vaseline on each " stud " location on metal frame, then set it down onto the rubber gasket to locate holes. Drilled rubber gasket. 2 man job to install window - need to get screws started from inside while pressing hard on outside. Once screws are all started, tighten a few turns alternating until all snug.
