My opinion is, for a carbureted engine which runs at 5-7 psi (or TBI which runs at 10-15 psi), AND you have a seriously pumped up engine AND run it at or near redline for long periods, you need 3/8" lines all the way from the fuel tank to carb. With port or 8-stack EFI which runs at 45-55 psi, the stock 5/16" lines will flow enough for any street engine.
Incidentally, a Ford TBI in-tank electric fuel pump will fit thru the stock sender fitting in our tanks and can be regulated down to carb level. It is also quiet. Just be careful- TBI pumps look identical to high pressure EFI pumps which CANNOT be regulated down to 5-7 psi without overheating. And once out of the box, neither are labelled as to the pressure delivered. I use my regulated TBI pump for priming the carb after the cars's been setting awhile.