I own a 1955 Dodge Royal with a 270 V8. Right now my temp guage is not functional, If I top off my radiator to full and run the car eventually it will start pukeing coolant out the overflow tube. And my coolant level gets low, would making and overflow tank be helpfull?

 

In 1955, that was how the system was designed to work. The radiator isn't 'full to the top' like you are used to on modern cars. There is a bit of an air gap, to allow for expansion as the coolant warms. Maybe get an IR thermometer, and see what temp your engine is actually running at. (or, fix the temp gauge. )

 

you still running 6 volt positive ground? If you've gone 12 volt, I'd put an electric temp gauge on it. Like another poster said, your radiator isn't a high pressure system and has an air gap at the top. About halfway between the top of the core and the fill neck is about right.