How long have you had the car? I too have an old AA/FC I am restoring. From what I have learned having the history on the car can make it or break it. I was lucky enough to buy mine from the original own and have all the history, including pictures of the chassis being fitted to the driver on the jig in Feb 1970.

Who's chassis is it? Do you have the SEMA number tag on it? That is the only thing you will probably be able to find a "production" number on. The bodies were made by many different people and unless there is an identifier on it somewhere, it will be a matter of luck finding any thing on it to be honest.

Good luck with it. If you need any help with anything let me know and see if I can assist you in anyway.