I'm doing a top end rebuild along with timing chain, gears, rings, gaskets, seals, etc. I have the engine out and want to replace the oil pump while I can. I've heard a lot about high volume pumps, but was just going to get a stock melling replacement. What are the benifits or reasons I should or shouldn't go with a high volume pump? 94 ranger 3.0 238,000 mi

 

No reason, flow above a certain level just goes back to the oil pan.

Oil pressure is "too much oil".
The oil pumps creates a flow of oil thru the filter and into the main oil passage, where the oil pressure switch/sender is located.
The oil continues on in the main passage and then goes into smaller passages and to the bearings and valve train.
If the flow of oil out of the bearings is less than the flow out of the oil pump then Back Pressure builds up in the system, that's Oil Pressure, too much oil from the pump.

Yes you want some oil pressure that means all sections should be getting all the oil needed, 6psi is OK at idle, 35psi at 4,000rpm
If there is too much pressure you can get a "washing effect" at the bearings which can cause bearing failure.
So the oil pump has a "ball and spring" pressure relief valve that will open and let some oil flow back to the oil pan, if back pressure gets too high.

If you were adding a turbo charger and need more oil for that then higher flow pump might be a good add.