BBC 468ci cooling problems

[pwrunt3pte]

hey guys, I recently got a 1955 GMC 1st series with a chevy 468ci engine. I'm having problems with the cooling system on this truck, and I'm begining to think the engine is junk. i just recently got the truck to idle and noticed coolant being pushed out the overflow bottle. I figured i needed to burp the system, so i left the radiator cap off and started the truck. the temp climbed to about 210 degrees and when the truck idled, coolant was flowing out the top the radiator because i had the cap off. when i revved the engine a little the flow of coolant would go back down and remain in the radiator. I turned it off and coolant poured out of the radiator like a guyser. I'm new to this so any suggestions would be appreciated