Actually, by law, I believe, you have to have laminated safety glass, not tempered used for the windshield. Tempered glass can be used for the side and rear windows. I believe that most model A windshields have a removable top piece. You didn't say what kind of car you have, but I think all windshields I have seen (open and closed cars) have a removable top piece. There should be some small screws on the sides and on the front (closed car) that need to be removed. The top should slide up and off. Sometimes the retaining brackets are rusted and soaking the frame in penetrating oil will help.