Jerr, the pump pulls water from the bottom of the radiator, pumps it into the block, from the block to the heads, and from the heads to the water cross over at the front of the intake, then to the thermostat housing and back to the radiator. If you run lines from the back of the heads to the cross over at the front of the intake (or thermostat housing) it will remove the hot water at the back of the head faster and help keep the temps at the back of the head close to the temp at the front of the head where the water spends less time in the head. If you don't run lines from the back of the head to the water cross over at the front of the intake, the water has to go from the back of the head, then across the head to exit out the front water port.

Even if the temperature differences between front and rear combustion chambers are small after the engine heat soaks at the very least it will help circulate water faster out of the heads. So, there is no downside to doing it other than the cost of plumbing.