I agree with Duey. If I fill mine anywhere near the top it will overflow as it expands. Just cover the tubes about 1/2 inch. You do need the thermostst, it restricts that heavy surge from the pump into the radiator plus lets your engine run at the right temp. Napa has them for a few bucks. Be careful not to twist off any of the three bolts that hold the thermostat housing to the head! I broke one and had to drill it out and retap it. Also gunk up the gasket with permatex #2 or such so it does not leak. Sometimes the housing is pitted enough you need a little more than just a gasket on there. Just a light coating on both sides worked for me.