Go with a new one. That original pad is almost 40 years old and is going to be brittle even if it has never seen the sun. Plastics start to deteriorate right after they are made and never stop. If they are exposed to the sun it will happen faster, but even if kept away from the sun it's still happening. That original piece might be okay for a museum car, but I wouldn't use it in any kind of car that's going to be driven.