Erik, there are two major things wrong. The first is the trim tag. It's a reproduction. There are several tale tell indicators but we don't go into detail because the people that fake these things also frequent these web sites. We don't want to give them any more ammunition than they already have!
The second is the date on the tag (12B). That's the second week of December, 1966. The 396 wasn't available in the Camaro until a month after your car was built.
I hope you didn't pay "matching numbers" money for the car. If you did, I would strongly advise you to march right back to the seller and demand your money back.
Ed