I had a project in welding class in high school where my teacher had me weld a tank on his son's '72 chevy pick up. I got an A in that class and am still alive. Fill the tank completly and have extra gas to make sure your gas leve is well above the hole. Tack weld a piece of mild steel over it then weld it all the way around atleast twice to make sure your not leaking. Remember liquid automotive gasoline won't burn and kill your bitch ***. Throwing sparks into the vapors will.

 

We burned a van down at work ------- around like that (I can elaborate if really needed) and I made a 2 gallon tank from a 1 gallon tank when I was 12 trying that ----. Either take it out and clean the ---- out of it so there isnt any vapors left or buy a new tank.