What else can I do to solve my overheating problem?
I've replaced my head's, water pump, thermostat, &
radiator and my v6 3.8L mustang still over heats.
could it be my oil pump?
The oil pump will not affect engine temperature. If it fails, so does the engine. Very quickly. Validate your temperature gauge with another measurement like a laser thermometer. Make sure the fans are working properly. A lean running engine will overheat. That is usually caused by failing fuel pump, clogged filter or injectors.