By circumstance I am currently refurbishing my '50 CJ3A windshield. It is the original unit, and I daresay it has it's original glass too:
"Guardian SafetyPlate
AZ Hi-Test WZ
50".
I'm suspecting the "50" is the year of manufacture for this glass??...
Anyway, I took the glass out of the frame and measured this:
Clear opening between the metal frame flanges:
49-7/16ths" X 13-5/8ths"
This measurement was very consistent all the way across and up and down. (It's a very good stamping whoever did it for Willys)
The glass measures:
48-3/4ths" X 12-3/4ths"
So the glass to metal gap was 7/16ths" on the top and bottom, and a tiny bit under 3/8ths" on each side.
Hope this helps.