sealant question
The birdcage, or structure that makes up the cabin of the car is all metal. As water leaks through and around it it starts to rust from within, and it can happen without you ever seeing it.
You need to remove the A-pillar trim, T-top trim, and kick panels and inspect for rust. Look as deep and as far as you can in every section of that structure looking for rust.
If you see some, where the rot has penetrated the metal, you have found a serious problem.
If your birdcage is free or rot then it really may just be a bad windshield seal.
Looking back on the Corvette history with the benefit of hindsight and considering the fabrication quality of cars today, it amazes me (as it did then) that GM turned out the crap it did during the C3 years. The service at that time was as bad or worse. Although GM is in serious difficulty these days, the amazing thing is that they're in business at all.






