If you have a sunroof or contemplating buying a Z with an existing sunroof, here are my suggestions:

1. Plan on getting a donor roof and graft it in to restore.
   
2. Look at the Canvas Retractable roofs (see link below).
   

Sliding Ragtop Kits Homepage

There is a picture of one on page 2 of their Gallery. These look pretty decent, so if you are in a position of dealing with a bad sunroof issue, it might be a solution.

That's somehow better?

That's somehow better?

Well, no. But if you already have a hole - seemed like good alternatives.