Going to move gas tank

[70CHEVYBB]

I have a cab tank but keep getting a strong gas smell at 3/4 and up. I have a 70 with only one fuel line going out. I have pulled the tank and checked it for leaks. I think I might just put a new tank under the bed, who's tank is a good one and any ideas on how to plug the cab after I pull the cab tank. I thought I might just cut the neck of the tank off and leave it sticking out of the bed. I'm looking for some good ideas on the filler neck also.