When pressure is low, it could be from the pump or other things. Although your ground could be crappy, I highly doubt it's causing a low pressure issue.
First of course, you need to rule out external leaks visually.
Next check the pressure of the system with the return line pinched. If the pressure comes up, you know the problem is with the return (regulator) side of the system. If the pressure does NOT come up, the problem is at the pump or before the regulator.
In the original Vortec engine, the fuel pressure regulator is under the plastic plenum on the side of the spider injector assembly.
If you have to replace the regulator but still have the original style injectors, replace the entire unit (with regulator) from Standard Motor Products.
8 cyl
https://www.summitracing.com/parts/s...et/model/c1500
6 cyl
https://www.summitracing.com/parts/s...et/model/c1500
FYI all units made are from SMP regardless of who's name is on them.
One other point. Usually when the Vortec regulator goes out, the fuel runs into the cylinders in the middle of the bank. I think the regulator is on the right bank side. The point is, check the oil for a fuel smell.
Don't throw parts at it like a CKP. You know the pressure is wrong, fix that issue first. Might as well say this as well. I have seen way too many fuel pressure gauges that were wrong. If you don't know for sure it's perfect, put it on a good running engine to see it's showing you the correct pressure for that engine.