I agree it's a 1946 date code as that 1939 block casting part number hadn't even been dreamed of in 1936...
Just because a block is listed in the Parts Book doesn't mean it was available. The example of the 1935/36 blocks comes to mind...in my almost 50 years of researching 1935's I've never see or heard of a later date code 1935 replacement block, the replacements were all 1936 blocks. I suspect the 1937-39 blocks were in the same boat, it just didn't make financial sense to produce the obsolete blocks when the later one would work and cover a wide range of vehicles/applications.
Mike B
