Fuel cap is spewing fuel

I have a 57 chevy truck, I installed a new fuel tank today. I put everything back perfectly except the vent hose. The vent hose that it had was cracked. Went to auto zone replaced the vent hose. I noticed that the old piece of hose had paper shoved into it. I put the new vent hose on, started the truck, went to the store to fill up. Came home, went inside. 1 hour later, leaving for church, there is fuel spewing from the cap! Fuel was coming out of the key hole, my paint was blistered. I immediatly took the cap off n u can hear the tank gargling! I went to church, when I got back the fuel was still gargling even with the cap off! Do I need to plug off the vent tube like it was? Isnt that what the vent tube is for? Mind u, I have replaced the tank before in this truck but the bracket behind the tank that connects the body to the floor made two little holes in the tank, so I bought a new one. Got any answers out there, thanks. Leo