Npt Ports 1 in. The regulator does not have threaded holes. The screws are self-tapping as they make the threads.
12-804 Adjustable Fuel Pressure Regulator with Gauge For Holley 1-4 PSI,3/8" NPT
12-804 Carburetor Fuel Pressure Regulator fit Holley 1-4 PSI 3/8 " NPT 1 in.2
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HOLLY FUEL PREASSURE REGULATOR/BRACKET 12803
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Holley 12-886 EFI PRESSURE REGULATOR Black Die Cast Fuel Regulator, 59.5 PSI