You shouldn't need the regulator at all. I'd leave it off or if you want to hide it mount it to the outlet of the electric pump. The mechanical pump does not require or need a regulator. In fact the red pump does not need a regulator either.
I had the Holley blue pump and that sucker needed a regulator. I've seen it go up past 9 psi before I backed it back just to see what it would do. You might want to have a gauge installed somewhere after the regulator. I found it quiet convenient to have.
