[Tom Wesenberg]

Tie a gallon jug to the hood rod and run a rubber hose from the overflow pipe to the jug. Run the hose to the bottom of the jug so the overflow can syphon back into the top tank as the radiator cools. You need a good cap gasket for this to work, and as Mitch said..............DON'T overfill the radiator. I fill to about 1/2" over the tube tops. The jug is just a temporary measure to see if and how much overflow you get.

I would also install a thermostat.