T Tops!
Most of the guys asking me for 2nd Gen Trans Am's want T Tops. T Top's command a higher market value than a coupe. If there is a concern about leaks, how much time is the T/A going to be outside in the rain anyway? Incidentally, we have a couple of Fisher T Top 2nd gen T/A's stored outside with no leak issues from rain. The 76 - to early 78 Hurst T Tops are the major offenders...
I recommend staying away from the aftermarket T Tops such as Cars and Concepts and American if you are concerned about top collector value. There is a limited marked for T/A's with C & C tops.