This is the inside of a standard $20 holley regulator. I knocked out the check ball and spring and fabricated a plug for that hole. Then I drilled a .180-inch hole in it. (bigger or smaller depends on fuel volume) With a Holley stealth two stage pump I pump between 80 an 125 gph and maintain 6 with one stage or 6.5 pounds with both stages pumping.
I used a slug of aluminum cut from an old x-acto knife handle (the big one) to fit the check ball hole, Perfect fit.
It doesn't have to be a perfect, leak tight fit since the diaphragm will always be open a little whenever the fuel pump is on.
Now the fuel comes in the bottom of the regulator, is regulated by the spring and diaphragm and goes out one of the side ports. Plug the other port or put a gauge in it. Open up the casting a little if you want to smooth the flow. The diaphragm in the regulators a Holley accelerator pump diaphragm.