Ok, maybe I figured it out. I have to cut through the seal in between the fiberglass and the metal window frame, taking off the entire frame, including glass.

Its tough as hell to cut through, but if I use the heatgun I can cut right through it.

88 4R, 350 V8, R150 5 speed Sold <...uot; />
97 4R, stock, daily driver
98 Sienna, kid and dog hauler, wife's ride