Whiskers & bumpers

I bought new whiskers and window bumpers ( the part that goes on the door uppers ) now I need to know how to get the old bumpers off my door uppers without hurting anything in the process. I have tried to pry them off and it goes well until the metal part starts to bend then I stop what is the right way to do this. I have the factory service manual and it has nothing. The car is a 73 dart sport.