engine serial number?

what you have shown are casting numbers, engine build s/n are stamped
to find those on the crankcase, look at the area between the alternator bracket and the very bottom edge of the cylinder head,
right at the split line where the block and cylinder head meet,
the block head face extends slightly past the cylinder head, there is a little shelf there,,that area is likly grimy, hard to see any numbers, but they are there.You can get in there with a paper towel and a long thin screw driver to wipe it clean.
I'll get a photo of the location and post it.