Hi grandpas te20
You mentioned about the number cast into the engine block of your 1930 model "L", that is actually the cylinder block part number. However if you look on the left side of the cylinder block, and up in the top front, corner you will find a flat machined surface, on which will be stamped also with the tractors Serial Number. Unless at any time the block has been changed, or a new cylinder block has been put in, in which case there will be no numbers stamped there.
Hoping that this helps
Alan T. Lewis
Christchurch
NEW ZEALAND