1990 350 w/ coolant drip

I have a 1990 gmc sierra(350 5.7L) that i just replaced the water pump. It is dripping from the front passenger side of the block rithg by the oil pan. There is a small divit with a hole at the end of it and i was wondering if there should be an expansion plug there? If it is not comming from there then it is comming from somewhere behind the AIR pump that i cant get off. Thanks for the help.