Do you have the correct 14” wheel covers? My dad has a 66 Formula S he’s owned since 1976, it’s his first car! I also have a pair of 66 Valiants so if you have any questions let me know.
Look on the back or top side of the glove box behind the dash, I found a build sheet there on my 66, my car actually had 2 of them...I have heard people also found them under the carpet, and behind the seat backs too. Might not hurt to look behind the side/door panels as well.