I too am interested in adding a key lock on the driver side of my '47. Here is an even older thread with a link to some pictures:
https://www.stovebolt.com/ubbthread...-drivers-side-door-lock.html#Post1072278
I noticed in this version of the mod Evan has the lock arm pivot in a different place than the passenger side, so the key slot location is not symmetrical.
The passenger latch mechanism has the lock arm sandwiched between 2 components. The driver side would have your add-on part above that area, but it could be lined up with the same key location.

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