Join over on this Pontiac forum (link below), and post in the 1977-81 Trans Am Tech section. Very knowledgeable people there would love to see such a great specimen. I had a 1970 Trans Am that we used Evapo-Rust on and it really did a great job on the underside of the car, once the sprayers were directed properly. njsteve is a member here, and over there, and you should look up his revival of a 1972 Trans Am survivor - his homegrown method of using rust remover was very effective.
Try and post a pic of your car's undercarriage too please.
http://forums.maxperformanceinc.com/forums/index.php
Here is njsteve's thread
http://forums.maxperformanceinc.com/...keepat&page=82