The following website link may be of interest to you, as I just used it to check my newest addition to my collector car "family" so hopefully it will work for the Thunderbird's too...it's interesting to put in your VIN number and see how many were made exactly like yours.
Here's the link: http://www.compnine.com/vid.php
Here's the link: http://www.compnine.com/vid.php