Bill, I would like to take block temperature readings with different volume pumps. I would bet that a lower volume pump extracts as much heat as a higher volume. After all its the time the heat is absorbed into the coolant and extracted that counts isn't it? The slower the water flows the more the heat is extracted?
Jack, the simplified heat transfer formula is Btu/hr = 500*GPM*deltaT, so a lower volume pump can transfer as much heat as a high volume, but with a higher deltaT. However, for engine cooling, we don't want a high deltaT between the top & bottom of the engine or the radiator, in order to minimise thermal shock. So you're "safer" running a higher volume and a lower deltaT, and your engine and radiator will thank you for it.
(Also, BTW, and completely off topic, that voltage divider circuit for the Hall Effect worked a treat, but unfortunately we found that the EDIS ignition definitely does not work with Hall Effect sensors, and needs a VR. Thanks again for the assist!)