You might be able to find another tank out of a similar Plymouth or Dodge.

I have heard, that sometimes radiator shops would repair gas tanks. You could ask around. They might boil the tank out and be able to solder a patch on it.

Several years ago I picked up a catalog from Performance Radiator. Beside radiators, they sell new gas tanks. They wouldn't have a tank for a 53, but their listings showed the dimensions of all the tanks they had. You might be able to find a tank from a newer car that would you could make work.