When I replace a tank, I like to plug the hole in the bottom of the tank and upgrade to the type of sending unit which has the fuel pickup attached to it, heading down into the tank from the top. It has a nice filter sock on the end of it and you will never have another issue of crud settling in the hole in the bottom of the tank, causing a miserable intermittent blockage of fuel.
The one you need is for a '54-'59.
You will need to route a fuel line through the floor, up along the front of the tank, then to the fitting on the sending unit. Copper-nickle line makes this chore a breeze. No bending tool required.