G'day Matt,
The Stovebolt website for old Chevrolet trucks says the following information about 1940 model coding... Hmmm this website does not like tables ... hang on a second .... I made it into an image and attached it.
Accessed November 19, 2016 from,
http://www.stovebolt.com/techtips/identification/Series
The same chart extends down to the US "War years" with different model numbers.
All these models may not have applied to Australian "Holden" assembled Chevrolets.
Kind Regards
Lionel