Let me see if I can confuse others.....The oil passages in a SBC engine block(s) are all the same, they are designed to be bigger than the volume the pump can ever pump out. The oil is circulated through the engine via a positive displacement pump. Oil pressure is created by resistance to volume. Max oil pressure is determined by a pressure relief valve at the pump.
If the oil passages are the same size, and the bearing clearances and other restrictions, i.e., lifters, are the same, a standard oil pump will pump X amount of oil at Y pressure. These restrictions, regardless where they are, offer a restriction to flow, the oil passage(s) fill up back to the pump, now the pump 'pumps' more oil into the passage(s), then the relief valve opens up, and bleeds off excess pressure.
The restrictions are smaller volume outlet than the pump volume capability. Thereby, when the galleys are filled, pressure is created.
Example: Start an older engine after sitting for 24 hours. Watch the oil pressure gauge and listen to the engine after it starts. You will hear a knock, whether it be a rod brg, or a lifter leaked down. While watching the oil gauge, you hear the knock go away, then SEE oil pressure on the gauge later. The oil pump has filled the galley void(s). Once its full, the oil pump pumps more oil into it and the restrictions limit the amount of oil bleed-off from the galley.
Now, R&R the oil pump with a high volume pump. All it does is pump more volume of oil due to its longer design as compared to a stock pump. The engine will still make the same pressure, we haven't changed the restriction sizes, thus the same oil pressure is seen on the gauge, or close to it. I'm now shoving more oil into the same space as before, therefore, I'm forcing more oil through the restrictions. Remember? restriction to volume makes pressure. So, now I'm pumping more oil volume, but haven't increased pressure, I haven't changed size of restriction(s).
Now, I decide I want a high pressure oil pump. I replace the relief pressure spring with a, for example, Z/28 spring. I've changed the maximum amount of oil pressure to be created. I haven't increased the restriction(s) size, or the galley volume, so when the high volume pump fills all of this void, its now going to force more oil into this volume. The relief spring is going to allow an increase in oil pressure before it bleeds off extra pressure.
Hopefully, I've explained or totally confused y'all.....