If that’s all the pressure you where seeing with the motor NOT under load , then that’s not good!

If I was seeing 5 psi under heavy load at 5000 rpm Then I could live with that with a motor making under 450 hp on the street.

Thanks Steve, we did observe some seepage on the AC-Delco fuel pump. Wondering if a RobbMC pump would improves things a bit?

I am sure one of his would!

Watch out if that pump is weeping!
It could fail with a internal leak and wipe out the motor, or leak external enough to wipe out the whole car!

AC Delco fuel pump

By the way, there where two aftermarket pumps that where screwed together like that.
One is the Holley brand, but it was chromed, and then the Federal Mogul / Cater brand that was not chromed like in your photo.
At some point the Carter pump changed over to a Nitrile Diaphragm that would live happy with 10% Ally cut fuel, but maybe that pump on the car was made before that change?

You can still get rebuilding kits for those 7900 series Carter pumps if you like.
And yes before anyone reminds me I do know that all Stock Pontiac fuel pumps up to 66 where screw together types thank you!