Flathead engine ID

[WQ59B]

I have a '40 COE, but the engine's bell housing date code is 11/1943 ('K 15 3'), the heads are 59AB, and the distributor is the diver's helmet style (correct for '41 & earlier). Sounds like a 'back-inna-day' rebuild using a number of parts, IMO.

I read that FoMoCo started production of engines for civilian replacement in late '44, Is the theory behind a late '43 block that it would have been military intended? Anything else noteworthy on these?