Either way you are going to need the rubber seal, it is auctaully what holds the back glass in place. I guess you could use urethane too, but I would not use urethane alone. I would try a glass place first, then if that didn't work I would try the stealership. If that didn't work I would buy a seal that had the same glass thickness and make sure it was longer. It would take a lil work, but it could be done.
90 Comanche thing. Exo-cage, tube bed, with a few other things done Here is a link to some pics of it
If you have to ask why... Its a truggy thing and you wouldn't understand