I don't think there ever was an L number assigned for a chocolate pleco. It does have a scientific name of
Pterygoplichthys scrophus, so use that instead of the L number. Here's more info on that plec:
http://www.planetcatfish.com/catelog/species.php?species_id=80
Oh, and as far as I know, there is no special L number if a species albino vs regular.