Mike,
My operating temps were around 170f at WOT and 150 at cruise and I had to use adjustable louvers to keep the cruise temps up around 150f in the winter.
You may get into a strange situation with no thermostat in the engine. The 582 thermostat acts as a two way valve which forces coolant through the bypass when the thermostat is closed and through the radiator when the thermostat is open. With no thermostat in the engine, the coolant can go through the bypass and the radiator at the same time.
I have never tried to run a 582 without a thermostat so I can't say how the temps would react. It wouldn't hurt to try if you keep a close eye on the temps. Just a guess, but if the thermostat is bad and permanently closed, removing it could only help. How much I couldn't say and there would be no temperature regulation.
I have always run a 50/50 mix of silicate free Dexcool antifreeze.
Another thing you might check is to pull the pump housing off the block and see if the impeller is OK and tight and no debris inside.
Bill.
