how rare is an 1976 duster 360 sunroof car !

Any late 360 A body will be somewhat rare. A hang ten car or Spirit car would be rare.

Sunroof, fold down rear seat, Buckets/console would make it even more unique.

If you are asking if it's worth $$$, it's not that desirable unless it's something very unique.

What are the codes from the fender tag.