If you have a carb ready fuel pump, don't need the regulator.
It's absolute statements like this that can cause confusion when trying to trouble-shoot.
I can truthfully say a 300 horsepower engine, when properly tuned, requires 150 pounds of gasoline per hour. Which is entirely true. If you can get Brake Specific numbers at approximately .40, that motor is going to use that much gasoline.
Let's just use the old 'a pint's a pound, the world around' method for a rough calculation and we see that comes to approximately 18.75 gallons of gasoline an hour. How many of you are consuming fuel at that rate? Anyone?
Are you confused yet? How many of you operate your 300 HP motors at maximum power output for one hour?
I do not have a mechanical fuel pump on the shelf that does not require a pressure regulator. So now, we need a definition for what a 'carb-ready' fuel pump is. After we define that, then we need to determine where the needle and seat fit into the equation, because they are certainly not created equal.
An engine utilizing a carburetor can run just fine with fuel being delivered via gravity and nothing else. If you can gravity-feed 150 pounds of gasoline an hour to a 300 HP engine, the engine will run just fine. And you know what?
The carburetor and engine will never know how the fuel got there. Shhhh, don't tell anyone.