steve,
6107328 is a block casting code that is actually cast into the block. That code indicates a 1953/54 248 GMC block.
The "engine ID or serial number" is pressed into the block after casting. It shows the engine size plus a serial number if the engine was installed in the truck at the factory; or, that pressed-in code is just the engine size if it was a factory replacement engine/block (as described by others in posts above).
