I realize that my reply may not be the exact answer you are looking for, but here goes.
1. You may not need to replace the entire roof; a few years ago I needed a replacement for the transparent roof on my 1995, and after searching for some time found an alternative to total replacement. There is a company in Bristol, PA (I know - very far away) that replaces the bad plastic (I think the official term is "lens") with an GM approved part on your own frame; good news here is it comes back ready to bolt on with no adjustment and the cost is approx $600 USD (that price was about 3 yrs ago for me). I would recommend this company to anyone who would like to keep the car as original as possible. Company is East Coast T-Top & Sunroof, 3950 New Falls Rd, Bistol, PA 19007. eastcoast-top.com.
2. If you replace that roof you will still have to deal with the heat on a hot day. I installed a product from Corvettecentral.com which is a dotmatrix shade that allows a limited amount of sunlight (heat?) to come through.