[Overdriven]

If you look at the stock 3500 express fuel pump module it has 2 electrical connections. One is for the fuel level the other is for power to the fuel pump. The weird thing is the stock fuel pump module has what appears to be a return fitting on it.

Either way, the ecm doesn't need to be connected to the fuel pump. In fact because the ecm uses PWM for the fuel pump it's better to have the fuel pump run off a relay and not the ecm. Most aftermarket fuel pumps don't like pwm power and will burn out, including Walbro's.

Your engine is setup for a returnless so there is no provision for a return on the fuel rails. This means you need a fuel pressure regulator before the stock fuel rails. This can be in the engine compartment or close to the tank. You can go aftermarket or with the popular vette filter/regulator combo. If you're planning on a high HP build, forced induction, you'd be better off swapping the intake or aftermarket fuel rails to go with a return fuel system and the regulator mounted to the rails or at least in the engine compartment.