fuel line

Changing one side without changing the other side will be useless. You need to change the sending unit, put 3/8 line on it, get a pump with 1/4" pipe inlet and outlet you can adapt down to 3/8 flare and replace the line from the pump to the carb with 3/8. My guess is, you probably do not need 3/8 line anyway. Most cars do not.