Both of my old gaskets, think they were originals, had to be cut. Car spent its life in the desert sun.....and I still think a bfh is the way to go....
I don't think you would want to do that to the back glass of a 67 cuda. I tried for about a week to find a NEW back glass for mine and I couldn't find one. My boss (owns a auto glass center) looked everywhere under the sun and couldn't find me one. I had to install my old one back in. My boss said even if I found one it would be $800 or more..... that's new of course.