I was looking at both my D4-12's today. The early model with the Craftsman Tecumseh has the oil drain pipe going out the bottom of the motor and the bottom plate of the frame has a hole cut out for this drain pipe to drop down through it. My later model D4-12 has the drain pipe coming out the side of the motor and the side frame has a hole cut out of it for it to stick through.
The NOS KD front head lights I bought back a ways had the painted rings instead of the chrome rings appear to have been original for the D4-12 tractors. I have seen at least 4 or more tractors at this point, that had these headlights on them.