Goes in as an assembly. Gasket on glass, trim placed in gasket.
get a 1/4in rope long enough to wrap around the gasket in the pinchweld opening, ending somewhere on the bottom of the gasket. Overlap about 3 in. and tape to the inside of the glass. place strips of tape around the glass,gasket and trim to hold everthing together while installing.
Place assembly into opening of truck, have someone on the outside putting pressure on the glass near where the rope starts and have them follow the rope around as you pull it. I also helps to use window cleaner as a lube to pull the gasket around the pinchweld.
If necessary have your helper slap the glass, open handed as the gasket starts to go over the pinchweld. This will help seat it. continue around the glass till the rope pulls out. Then slap the glass,open handed till the gasket fully seats itself.
These are a real PITA so us patients went doing this, it might take a few tries and you"ll learn from each try.
Good friggin luck,