I did the same thing as Chuckthetruck, bought glass from ChevyDuty and used bandclamps to press the glass into the frames. Be careful not to overtighten the clamps or the glass will seat too deep into the wingvent frame and leave a gap between the vent glass and the guide post (doh!). :p

1955 First Series GMC 250 1-Ton Panel
In the Gallery
Mr. Hedgehog - Follow the build
If you can't laugh at yourself, I'll laugh at you.