Is this a Model B engine? B's used a fatter oil filler supposed to reduce oil fog escaping into the engine compartment. It looks a little like that's a 3-bolt water pump which Model B's had. Is there a letter C cast on top of the head, a little to the northeast of the distributor as you look down on it? And is there a mechanical fuel pump on the other side, down and to the right of the carburetor (or a block-off plate added later)? But I'm really curious about what appears to be a three-blade fan, which I've not seen before. More pics would help.
Fearless