My comment on the mirror is not about size, but location.
When the mirror (original) was mounted to the windshield, when I raised my arm with my elbow on the arm rest, my fingers would hit the mirror and knock itoff the windshield.
I glued it to the windshield so many times, the windshield finally cracked.
So, when I restored the car, I epoxied a piece of aluminum to the roof so I could attach the mirror to the roof, which moved it up by about 5 inches.
You actually get a better rear view with the mirror raised and the windshield is still pristine.