When the lamination seperates, that's it usually. Either replace the glass or live with it. The window gaskets are availiable.... I just bought one for my `74 Dart from Jack's for $85 I think, but a word of warning: CHECK the gasket against your car BEFORE you pop out the shield. When I bought mine it was too tall, like it was for a 4 dr. or another application, maybe a convertible. Being the trusting person I am, I just called in the glass guy and when he was putting it all together he noticed the problem. He had to section the gasket at the top (which pissed me off...) to get my car together. When I called Jack's to let them know what happened and to ask, or warn, them about the problem I was greeted with (and pissed off even more...) the usual: Did the glass guy know what he was doing? Are you SURE it didn't fit? We've NEVER had this problem before.... Are you sure you bought it from us? And so on....
Rant aside, the gasket and glass is out there.