I did a restoration on a '78Z with badly cracked interior panels. I pieced together as much as I could and used a plastic body filler by U-POL-stronghold 76. It fills great and can be finished with primer/paint. I've seen other owners use plywood and paneling and make speaker boxes to replace the panel. My customer wanted everything stock so I used the U-POL product and was very satisfied with the result.
OK, thank you for everyone’s input. I see what the problem is now, being new to Z ownership, I didn’t know how the rear panel was attached. I wondered how you got it off so easily. The previous owner riveted it on! Any suggestions on how I go about rectifying the situation? Thanks again for all your help, much appreciated. BTW, my car is an 8/71 Money Carlo red 1971.
That panel you're referring to is called the tail light surround panel. Try using an 1/8" drill bit and drill out the rivets. They take a special reusable plastic rivet that is similar to the interior rivets that are used on these cars. I carry both the interior rivets in all the stock colors and the smaller rivet for the tail light surround panel. The actual color for that panel is not the Ford color someone mentioned. Find some SEM brand paint and use #39033 Charcoal Metallic, it's a very high quality paint for a rattle can. It's available at most automotive paint stores. That same color is also a perfect match for the original hubcaps and the front grille. Z man of Washington