I’m building a couple of 502 gen 6 Efi engines. They run a Holley low pressure fuel pump. Then a high pressure pump ontop of a fuel cooler / vapour separator tank on the top / rear of the engine. The VST tanks are blocked. So wouldn’t cool anyway with no water going through. Iv stripped them and they are in a bad way. Looking at these numbers they are 120psi. Question is can I just run with no cooler. Vapour separator ? The tank has a float inside attached to the inlet manifold. ? So if I can find 2 new 120psi pumps. Run inline. Will they be ok ?

Ditch all the VST stuff. 120psi pump means nothing. VST systems run at about 30psi.
Get a marine efi pump that flows enough gph...like.... Mallory Ignition 11106M Mallory Marine Electric Fuel Pumps | Summit Racing
Then get a fuel pressure regulator and run a return line back to the fuel tank

Thanks. Shows not in stock. I will see what’s available similar in uk.

have this available in the UK ?

https://www.demon-tweeks.com/uk/aem-...mp-aem50-1009/

You can run without the VST and cooler but they help prevent vapor lock. If you use two 120 psi pumps inline, make sure the first handles flow and the second meets EFI pressure.

Techinically not marine rated, but should work fine. Then use this regulator or similar Buy AEM Electronics Universal Adjustable Fuel Pressure Regulator - 25-302BK | Demon Tweeks

If you don't have a port on your fuel tank to run a return line to, you can T into the fuel filler filler tube.

BTW, there is a wiring diagram in this thread about how to safely wire up an electric fuel pump. Belt driven raw water fuel pump assembly - Offshoreonly.com

nice. Thanks for the info.