I filled up my 85 e150 with coolant yesterday, drove it, got out and noticed it was spewing coolant from a little hose that comes from right next to the radiator cap and goes down around the radiator and goes nowhere and dosent have a plug or anything.

Should this be plugged? Should it be going into an overflow tank? How is my cooling system staying pressurized with this little hose letting extra coolant drian out onto the ground?

 

begin with a new pressure cap.

 

I agree on the new cap for starters. The overflow tank is entirely up to you. It is required at the drag strip for obvious reasons but wont hurt anything if your radiator barfs a little on the street.