At one time there was an individual on this site who went by "Wingnut". He would be able to help you if he is still around. Bob Lee Archery has stated in the past that they cannot answer or will not answer questions about Wing bows. Guess it was taking up way to much time.
One thing you would need to know is it a pure Wing Thunderbird or is it marked AMF, etc. I know there are Wing collectors on this site. Also,if I'm not mistaken, Traditional Bowhunter Magazine did a piece on Wing a few issues back. Good luck.