Assuming that everything else is the same, couldn't you just Tee off the fuel supply and fit a pressure regulator between the supply and the return pipe, We are working on a Ulysee with a returnless system and all it has got is a Tee off the fuel supply line ( At the rear of the vehicle near the tank) returning straight back to the tank and the pressure reg looks as though it is in the tank sender/pump unit. ??