Try to find out what year this model t is. There's a number stamped in the wood BF31818. The motor number isn't legible. Electric starter, metal seat frame, coil box under dash. I'm thinking it's an 18
The casting no. should be about where the one in the picture is. Some later blocks had a round no. insert. The last no. is the year - this one being 1917.
Sometimes the serial number can be brought back by using a liquid dye penetrant used by piping contractors to detect cracks in piping systems. The slightest indentation will show up.
Just a thought.