Front quarter vent window removal.

I'm tackling the same job on a '51 Pacemaker and changing cracked vent windows while at it. There might be a better and easier way to accomplish the task but here's how I approached it:

I decided to remove the entire vent frame assembly channel out of the door and took it to my local glass shop (again my glass is cracked). Removing the chrome frame that encapsulates the vent window involved drilling out the two small rivets in the "upper pivot pin" and removing this piece. The frame has a barrel that pivots/rotates on this pivot pin (see pic below). Removing the pivot pin "frees" the chrome frame + vent window to slide out of the old rubber and provides unfettered access to replace it with new rubber molding. Once the rubber is replaced, slide the chrome frame + window into it, place the pin into the barrel and maneuver it over and onto the frame and re-rivet (or use small sheet metal screws).

Hope this helps rather than confuses things.

Pic of Pin and Barrel:

That's a hard job dude.