Is there a proper way to cut gl in my own garage?

i have a 1976 AMC Pacer with a busted out driver's side window. It has the optional vent window, which many of the cars did not. I can only find gl for cars without the vent window. I want to know if there is a way i can cut the gl to make it fit for my window. is this possible? with a butane or propane torch, and maybe a knife of some sort.