Some of the water pumps have a universal fitting on the rear that have to have a brass fitting tapped into them kinda like a small freeze plug.

Some cars do not need the fitting because they have a hose that bolts on there, but others have to have the plug tapped into the hole, make sure you ask when you get the pump.

I am talking about dealership M/B pumps.
Aftermarket ones may not need the plug or have the hole in the rear.