Hey fellas I guess you don't know about 36 windows having a frame with screws up till 1941 they had a pot metal frame holding in the window and rubber.

Best way is to have help hold the window with the glass and hold the frame up and put enough pressure to mark the rubber where you need to drill the holes for the frame screws to thru just make sure you have the window where it needs to be in relation to the opening then you can drill your holes thru the rubber and screw it in.