Anybody use one of these water pumps?

Those are also very good pumps. IIRC, FlowKoolers max out around 3500 rpm before droppping off. The other thing I like about the PRW is where the housing is also shaped like a matching volute to the impeller to channel water into the block. I’m thinking the Milodon is also made a lot like the PRW, too. I also suspect these pumps work better over a wider range of rpm with under driven pulleys, being they would probably start to cavitate when rpm is increased after reaching peak flow.