I'm trying to figure out what fuel pressure regulator I need for the truck. It has a 5.8L 351 in it (not sure if Windsor or Cleveland) NOT EFI. My regulator recently started spitting out gas onto the engine. I just can't find which regulator I need, Holley 12-804 or Holley 12-803. Any idea where I can find this stuff out? The truck did not have the manual with it when I bought it.

The carburetor is a Holley 4 barrel 1850-3.

 

I don't think your engine if it has a carb has a "fuel regulator".
If the fuel is flowing out of the carb ,chances are the float is stuck and not shutting off the supply of fuel from the mechanical fuel pump. Can you check and make sure the fuel is coming out the top of the carb or the bottom. There would be different reasons for either source.

 

The part looks just like this one.

Amazon.com: Holley 12-803BP Fuel Pressure Regulator: Automotive

It is leaking gas out of the top.

 

I wish I could be of more help to you. I have never seen any type fuel pressure regulator on any carbureted engine. You may require one if you have a high pressure /high volume fuel pump. All of the holly carbs I've worked on never had a need for a fuel pressure regulator. Hopefully someone with more experience with this type system will reply.

 

I finally figured out why it has the pressure regulator. The truck was originally fuel injected so it has the high pressure pump as well as the pump in the tank even though it now has a Mustang (5.8L Carb) engine.