An electric water pump can be put anywhere in the system.  We've found that the Davies-Craig unit fits nicely right below a left-inlet water pump (with guts removed).

Engine Flow:

The coolant is drawn from the bottom of the radiator by the water pump which delivers the coolant to the cylinder block.The coolant travel through the cored passages to cool the entire length of each cylinder wall. Upon reaching the rear of the cylinder block, the coolant is directed upward into the cylinder heads, where it cools the combustion chambers, valves and valve seatson its return to the front of the engine.The coolant from each cylinder head flows through the water passages in the intake manifold past the water thermostat, if it is open, into the top of the radiator. If the thermostat is closed, a small portion of coolant is returned to the water pump for recirculation. As far as the the plugs, make sure that beside your upper radiator hose, you have a small 90 degree hose from the thermostat housing to the top of the water pump. On the passenger side of the pump will be a nipple which connects to one end of the heater core (supply), the return from the heater is located on op of the intake manifold just behind the thermostat housing and beside the water temp. sending unit.

The plugs on the back of the heads are from smog ports of a late model 5.0, unless you plan on using the engine as a late model with computer, don't worry about them.