Jffr, I don’t believe your experience with the Edelbrock waterpump necessarily means it doesn’t flow as much coolant as the Flow Cooler. Cavitation is a complex issue. It could be the Elelbrock flows more coolant than the Flow Cooler, right up to the point where it cavitates. It may be that the Edelbrock simply reaches a point where it simply isn’t possible to pull more coolant through the Pantera’s cooling system. The Flow Cooler might not reach that maximum CFM point until a much higher RPM.
Years ago, I spoke with an engineer at Stewart about the Pantera’s cooling system. He mentioned the exact situation I just described. He said a great waterpump might be worse than a poor one due the the flow restriction caused by the physical length of the Pantera’s system. His advice was to remove as much restriction from the cooling system as possible. He said this is one car that should never use a multi-pass radiator! He also described the Pantera’s waterpump as a cavitation machine!
As far as the Pantera’s coolant bypass is concerned, it’s there for a reason and most modern cars use similar systems. It gives a more even, gradual warmup. It helps to eliminate hot spots in the heads and the heat shock that’s so harmful to aluminum radiators, when the thermostat finally opens and lets boiling hot coolant to flow into the rad. Some owners may have zero trouble without a bypass but as a rule, any 351C should have a correct and functioning coolant bypass system.