Old Hot rodder

I have a 74 Plymouth Scamp that I sourced without an engine, but I have a 440 in good shape and a 727 that I'm just dieing to do something with. sounds like a marraige made in heaven. Meanwhile I have a few rust issues to deal with. One is the back window and the other is the windshield. I want to get the back window out without breaking it so I'm thinking, cut the rubber. Any thing wrong with that? It's going to cost me about $130.00 for a new gasket if I do but do I have an option?