heater hose question 48 willys pickup

I have installed a re-built motor in my 48 willys pickup. I am trying to hook up the heater hoses, but only find 3 hose connections. 2 on the firewall for the heater core, and one on the water pump. when I got the pickup, the hose off the pump was plugged off and the heater core was not hooked up.
Does anyone know where the 2nd hose hook-up is supposed to be on the motor? There is a plug on the top of the head towards the firewall that has always been there since I have had the truck. Could this be it? I have the flat head 4 cylinder motor.

There is a plug on the water pump and a plug on the rear of the head to make the flow complete.