Where are the body numbers on a 66 Barracuda?

I believe the only matching item that shows it's a 66 engine is on the drivers side just below the head and 1966 273 should have the letter B. Mine starts out as B273 and I was told B is for 66 if there is someone out there with a 1965 there's should start out with a A273 not really sure on the 65 but this is the way it was explained to me.
Bob