Every car when broken down by the factory options can be considered 'low production', however that does not make the car 'rare'. There are tons of obscure combinations of options that can make any car very low production combinations. For example how many 71 Cudas were built with 383, autos, FC7, V6X and a block heater? Fools game.
When considering your car with a 383, automatic, and FC7, to me, it is not what I consider rare. If you are talking about Hemi 4 door sedans you are talking about rare vehicles.
Enjoy your car as it is pretty cool.