273 Commando or Not?

I bought a 65 Cuda last spring when we removed the trim and glass we found the factory stripe. I really don't much about these cars but I learned that it is a Formula "S". How can I tell if my 273 is the Commando motor without taking it apart. I did find some #'s on the driver side of the block on front below head , A 273-9 2 then below the is an A stamped. Then on pass. side of block there is a D N and then 7 3 64.m It does have a 4brl carb.
Thanks Jerry