I've had engines with and without that drain fitting, not something that's used much - one should be available at a local parts place or rad shop, it's the same as the drain on most of the old radiators - it does as well to pull the plug you have and flush some water thru, sediment does tend to collect in the passages down there - or if you store the truck long term in the cold you can drain the block there to be safe against freezing
Bill
