Where is the engine serial number on a 2004 f-250 6.0?

The engine serial number on a 2004 Ford F-250 with the 6.0L Power Stroke diesel engine is located on the driver's side of the engine block, near the front. It's usually cast directly into the block itself and might be somewhat difficult to read depending on the condition of the engine. You'll likely need a flashlight and possibly a wire brush to clean off any grime before you can clearly see it.