Someone disconnected hoses to heater box on back side of engine and ran from back rail back down to return on engine; I am reconnecting; which is in and out!
Rich

 

Hi RB9421,
This is for the 420 built of off the S-type and not the larger 420G/MK X. The plumbing maya or may not be the same for the 420G/MK X
From looking at the parts manual for the 420, the heater in comes from the intake manifold to the heater valve and into the lower heater core tube. The return goes from the upper heater core tube to the water pump. Possible reasons the the heater core would have been disconnected is that the multiple pipes used to connect it to the engine had rusted out, I don't know if they are being reproduced today, or the heater core leaks. I would try to have the heater core pressure tested before installing the hoses again. You don't need coolant leaking into your car.