64 cuda driver's side mirror

Hi 64 Cuda owners! I need to replace my driver's side mirror. The one that came with it when I bought it is round. The center to center of the screws is 3 1/2". I'm not sure if this is one that came from the factory. If not, i'm not about to drill new holes. Does anyone know where I could purchase one with 3 1/2" center to center holes??