Found another '66 Formula S but I have some doubts...

We just did this same search on another Barracuda. Look at post #80 on this thread:
Is my car a Tag Job? Barracuda Decode... | Page 4 | For A Bodies Only Mopar Forum
This will tell you if all your body number stamps match your Fender Tag. After that it's decode all the equipment and try to tie all the information together. Broadcast sheet by any chance?