High Volume vs Standard Volume Oil Pump

The pickup diameter becomes a restriction. It's not in most circumstances. The problem is the HV pump reaches that cavitiation point earlier. But - I think it's still way above the rpm range of most street cars. The real problem is with the block and the lower end clearances. If your clearances are tight, and the lifter bores are tight, and the passages in the block are stock size... The HV pump's output is far higher than the system's "leaks". Remember that pressure is the combination of volume and restriction. So the HV pump pushes a lot of oil through the bypass which adds heat to the oil and robs a bunch of power. IMO - that's how the oil pump drives get sheared... the resistance is so high, and internal resistance is less power to the crank.
To the OP - if the clearances are good and less than .0025 or so, you don't need an HV pump. However - the factory stock pump has a bypass relief spring that releases at about 50psi. You do want to make sure you've gott hat 10psi per 1000 rpm deal - so add the MP High Pressure relief spring or run the HP pump.