My first thought is to remove the thermostat so I can run 100% water through the entire engine water passages to completely remove and flush the old mixture out. New radiators seems like a good time to replace the thermostats anyway, while "I'm at it". Thermostat removal required to allow the fresh water rinse throughout the engine, otherwise the thermostat would close, and the rinse would not be as effective. Am I missing something? Also I want to put in the absolute best thermostat available. Stant? Or??