Ed i did a 35-6 chevy decades ago, so my memory not to clear. I think with wing open you spread fame up top to clear upper pin, then just pull up to clear the bottom pin/drive post. Runs in my mind some different years may have a couple rivits holding lower in?
Closest i've found on youtube,
type "42 to 48 chevy vent window seal replacement"
I think yours may come apart similar. Best i could find.