The link that Randy provided to the Hemmings/Chevytalk site is for US engines. The Canadian numbering was similar, but different. Elsewhere on that site is a huge Word document containing info for Canadian engine serial numbers.
The info around '40, '41, and '42 is a little unclear in that document for the T-prefixed 216 truck engines, but I think that 3795778 may have been sometime in late '41. The Canadian engines may have continued use of the '40 style parts longer than the US engines. The Chevy 224 engines used in some Canadian vehicles (GMC trucks and Pontiac cars) would have a different prefix.
My parts books show the 598309 pump as being from a '37 or '38 with pulley number 838764 or from a '39 or '40 with pulley number 838905.
