Since I was there, I put in a high-flow 180 degree thermostat and run Red Line "Water Wetter". If you look around in here, you will see differing opinions on the matter. This works for me. 383 stroker (dyno 344 hp/434 ft. lbs. with stock exhaust manifolds) and stall converter. Kansas in June stayed at 170 degrees at 75 mph, occassionally to 180 degrees in low speed, in town traffic/idling.