Does the rear window require a gasket to install the window or does it use the rubber glue?

There is no rear window gasket. What you want is 5/16 butyl (sp?) tape. This will raise the glass to a good height so you can get the trim on easier.
I am pretty sure the correct thickness is 5/16 - can another member confirm?

The rear window actually uses black urethane and you can have a local 'glass guy' do it pretty cheap. Just tell him how thick you want him to put it on. I've seen 'em lay 2 beads of urethane (one on top of the other) to get the proper height/thickness; especially on trucks and SUV's

we tried urethane and the tape worked better

5/16" wide ribbon seal (also called butyl tape) is the way that the factory did it. Black urethane is what newer cars use and what most glass guys carry in stock. They say they can make it high enough for the trim to sit correct but I yet to see that happen. They also try to tell you that the urethane is better and your window won't pop out....LOL... my 30+ year old car still has it's glass and the Butyl tape is still holding fine. Good luck...

Thanks guys,

I first used butyl tape on my coronet back glass and it leaked like a sieve. Cut it back out and used ureathane and it fits perfect with no leaks.