46 Texaco,
Did you see the term "Liberty Series" in a document or on a website?
There were series-names used for some of the Chevrolet trucks before 1940 and after the Advance-Design series, but, as Denny very nicely described, GM/Chevrolet did not use an official series name from 41-46.
There were Liberty trucks in WWI but it was not a truck from a specific vendor.
http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=8126