Personal experience from the 100s of pumps I've built.
If you start with an aftermarket chinese cover, the gears are countersuck so it's not possible to lock them up (or set proper endplay). Since his engine is unopened, I'm going to assUme that it has a GM cover on it therefore the gears protrude above the casting. If the protrusion is greater than the compressed thickness of the gasket, then the pin is pulled.
The engine has plenty of torque at idle to "self clearance" the pump and fill all the oil galleys with shrapnel and shavings.
It would be a damn shame to lose an engine, turbo and radiator fixing a low pressure problem that doesn't exist.
That 25+ year old timing chain on the other hand needed to be replaced a couple years ago. (and the pan cleaned out from the teeth that have already broke off).