Don't know much about 76 Nova's, mine was a 63 (Chevy II) and a 76 Omega. So I guess I have to ask have you checked you local bone yards? Are NOS parts available from other than Ebay? The fiberglass would probably work. Standard tail/brake bulbs should work fine without heat probelms, but stay away from the newer ultra-brite bulbs as they tend to have more heat.

You might consider LED bulbs, they start at about $10 each, use the standard socket mount, and are low heat output. I run the LED bulbs behind plastic teardrop lenses with no problems on a 39 Ford.