According to my "Chassis and Body Parts Catalog", I have to agree with the assessment that it's a 1958-1962 block.
The engine code "F0719J", according to the book, is a block, cast in Flint, on July 19. It was originally used in a 3100 - 3800 truck with a 3 Speed Transmission.
There might be a date code behind the starter that could pin it down a little closer for you.
