what the HAY! sunroof?

V3X is the code for the canopy vinyl roof.

M51 would be the code for the sunroof for 1971.

http://www.hamtramck-historical.com...lershipDataBook/1971/71_Valiant_Duster_22.jpg

And yes, they are out there, not a plentiful as the steel sunroofs, but they do exist.