The driver side remote mirror on my '72 Supreme is NOS and in perfect condition. What can I do to preserve the chrome to keep it from pitting?

 

Don’t drive the car through the salt or spray it down with some oil

 

Clean it thoroughly and apply something such as wax on the chrome to seal/protect it from the elements.

 

Would chrome polish work?

 

Yes. Wenol red works great, as do Simichrome and Blue Magic. I've successfully used Meguiars paint polishes on chrome too. Flitz is good stuff but hard to find in some areas.

I prefer a paste or cream metal polish as it's easier to keep off surfaces where it's not wanted. Get it cleaned to where your buffing cloth doesn't show any more residue and then use a good wax to protect it.