Mines a 41401-3 the smallest 1200hp unit, but on 18v it still pushes 420ltr hr at 84psi fuel pressure.
Im using a boost a spark to pump the volts up, off boost the speed control relay disconnects the control signal from the Reg and switches the control terminal for the pump to earth for minimum pump speed, once it comes onto boost the boost a spark pulps up to 18v and the pump gets full speed control. This is all geared around reducing return flow.
With a big mechanical reg you could just use a Hobbs switch to control pump speed.