[bestgenman]

I remember reading in the AH manual that the circulating pump located beside the AH unit sends AH heated coolant to the engine and when the engine is running the coolant flow is reversed by the engine coolant pump. The manual instructs the user to turn off the AH circulating pump while the engine is running for optimum performance.

I also remember on my 89, there was a pump located in the front end near the back side of the headlight bucket to assist flow to the heater core. it was activated when the heat control was set for heat. If you were to install a pump, whether in the front or rear, in the loop to the heater core it certainly wouldn't hurt.