[elmariachi]

Don't discount that 160 t-stat being a contributor. Most HP V-8s run at 185-200 normal operating temp. So your 160 thermostat opens once as the car heats up, and never closes again. That's not what you want. If it isn't cycling open and closed over and over then the water isn't staying in the radiator long enough to get that 35-40 degree drop, its just racing through. Car then overheats and stays that way. You need a 180-190 t-stat so that you can create the "heat exchange" properties between the engine and radiator up near the proper operating temp. A weak fan or poorly constructed shrouding can cause this too. Home Depot sells a Bosch handheld infrared temp gun for $40 that will help you nail this problem down in about 10 minutes. Start by measuring the difference between the top hose entry and the bottom exit.