Hey Vettech, I couldn't find all of the codes in my NCRS book, so I hope that the below is helpful.
L48 California was only produced in 350cu, 275hp and a below 4kft turbo Hydra-Matic with 3:55:1. The engine code should be CLR.
NA6 represents High Altitude Emissions (with a $33 retail adder, however none were recorded to be produced).
C60 is air con (37,638 made)
NB2 represents???? Nothing listed.
In summary, you will most likely have C60, but unless your car is an off production freak, it won't include the NA6 option.
Does that help?