"Things in the engine compartment seem to indicate that it might have a later engine (and it has been changed to 12v). Codes on the engine will help ID it."
It looks like there is a 12v system ignition-resistor on the firewall. If that is a ballast resistor, this was just an observation that the electrical system has been changed.
The valve cover does not help to ID the year of a block. They were bolt-on interchangeable from 54-63 and there were at least 4 styles of 4-screw 235/261 valve covers.
If the casted-body of the water pump is entirely below the head, it is a 1955-2nd or later 235/261.
As others posted above (I think), the door-post code (if it is the original plate and the original code) indicates the cab was assembled in 1954. I have not carefully studied all entries above, but I do not think that an engine ID has been posted in this thread?
