Leaking thermostat housing, best gasket???

a couple things i have done. deck the intake side with a 100 grit block sander and make sure it is flat. do the same to the housing. i have had great success with no gasket and high temp orange permatex , a thin layer on both sides and let set up for about 15 minutes. i have also done the same with a gasket but you have to completely cover the surface area with the gasket sealer. do not over tighten the bolts as this will cause a slight warp. i also use good sized washers to distribute the pressure.