[RalphM]

There are no serial numbers on blocks With the integral bell housing.. All Transmissions were stamped from the factory with the vehicle serial number that matched the frame. But you can narrow down the year by features on the engine block as the fellow that sold your engine did.
Now some 49 to 53 flat head blocks with a separate bell housing did have a date code stamped into the top of the block in the rear near the intake surface. I say some because they all do not have it.