I went to change the termostat in my truck

I went to change the termostat in my truck. It looked like it didn't have a gasket before so I cleaned up the surface of both areas and just used the rubber seal I bought for it. Which is what it looked like what was on there before. Well it leaked badly. I had also bought a gasket. So my question is this, I have permatex ultra blue and # 2 form a gasket. Will ether of these work good or should I go back to town and get the one for termostats. Thanks so much. John