Your buck tag photo was very cool. My '66 GT fastback is also a Metuchen car, has the same scheduled build date and same DSO. My consecutive number is just over 7000 units higher. I'd be interested in seeing some of the similarities of our two cars. One thing you may find which can cause some confusion are late '65 parts on the car. Document, document, document!
Good luck with it, looks like a fun project.
p.s. I'm really curious as to whether the car has '65 style ceramic GT badges or the plastic '66 style?