This is on a 50 year old gasoline powered tractor. The gas tank is right in front of the steering wheel. The fuel gauge is mechanical, and it's not working. It bolts onto a 2" hole at the top side of the gas tank. I took off the gauge, and the cork gasket more or less crumbled apart. Now, when the tank is half full, the gas sloshes around and comes out of the crack between the gauge and the tank. What's a good kind of sealant to put between the gauge and tank that is impervious to contact with gas?