Fuel Return Line - Do I Need One?

I need some help as I'm starting to get parts to redo the entire fuel system. Do you need a fuel return when running a mechanical fuel pump? I'm looking at a 3/8" sending unit and feed line with a mechanical carter fuel pump and a 750 Carter Comp Series AFB on a 451. The sending unit has a 3/8" feed and 1/4 return line, would I just cap the return at the sending unit. I'm a newb when it come to carb's, only work on fuel injection at work. Also, is it just the pump that determines fuel pressure, (I know I need to keep it below 6 psi) or will I need a regulator? Any help is greatly appreciated. THANK YOU