Return line should be bigger than feed line so the the regulator does its job. An equal size return line can cause x amount of pressure by itself rendering the regulator useless

Placing the regulator after the carb insures fresh cool fuel at all times to the carb

Its not about the fuel system making the car faster. Its about the life of the pump. Not having a single fuel related issue when its 1 million degrees outside. There is always someone from Michigan that says its a worthless upgrade. But down in the south it's the best thing you can possibly spend an extra $100 on