Corvette info needed
 

I´m going to repaint my -74 L-82 Corvette in it´s original colour. It´s a late -74 built car that I believe was Bright Yellow from the factory. The -74 paintcode for this is 946 and the -75 code is 56.
The trim tag says:
CHEVROLET N05
TRIM 400 56L PAINT

If it uses the -75 code, what does the L mean ?
Do you know a good source for decoding Corvettes ?

Thank`s
Anders