Hi Brian,
Try this one. 1940 Maple Leaf Truck Series 16-40/ E6, E7, E8, E12.
Also 1940 Chevrolet Truck Series 13, 14, 15. which has GM part number 1116291 and NASCO part Number 1116278.
These pages came from this book which was "Specially compiled for the AUSTRALIAN MILITARY FORCES" by the National Automotive Service Company a division of General Motors - Holden's Limited.
Whilst this is an Australian publication, I am sure that it refers to the USA and Canadian General Motors vehicles.
Regards Rick.