Webers required less than 4 psi pressure. The 720 carburetor doesn't.
The regulator goes into the fuel line after the pump.
That being said, my 1200 has neither the regulator nor the relay
Both are a good idea, but it will work without it. The carburetor float needles may handle the higher pressure, but aren't guaranteed.
7 psi
http://datsun1200.com/modules/mediawi ... ?title=Electric_Fuel_Pump