you still need a corrosion inhibitor, if you ever try to take apart a sb ford or 385-429 -460, the front timing covers corrode badly with water only, Farmers summer equipment that used water only. they drain them and let them sit the rest of the year. a lot of replacement water bumps use sheetmetal impellers. they also will l rust and I have seen loose ones , broken free from the pump shaft.

Did you burp the system? air can get trapped in the heater core. loosen the top heater hose slide it back a ways. drill a 1/8 hole thru the tube one side only. Start it up and let the air out. when you get coolant slide the hose back into position and tighten the clamp. you defininatly need a shroud . a good fan will pull air off the road instead of thru the radiator.