Fuel system upgrade quetsions!!

for equality of fuel supply (and pressure) to the rails you would need a y-block with feed line to each rail, then from each rail to a bypass type regulator with the return back to the tank.

you could probably run a system like BBK (5010) (that adapts to the stock rails but using your aftermarket stuff), the regulator would have to hold pressure for the rail that doesn't get the direct fuel feed