This might sound like a silly question but what is the difference between high vol and high pressure oil pumps? I just rebuilt my 383 it has a stock oil pump and at idle the oil lights flickers give it gas and the light goes out, I have read about this and it seems to be a common problem or issue with big blocks. Thank you any help is appreciated.

from a design standpoint the "high pressure" pump will have a heavier spring (than stock) in the relief valve. the high volume pump will have a pump body and rotors that are taller. these are positive displacement pumps (as opposed to centrifugal like a water pump) which means they pump a specific amount of fluid for each revolution. this is why the pump with taller rotors pumps a higher volume. the relief spring controls the maximum discharge pressure of the pump by spilling any excess above it's setpoint back into the suction of the pump, so essentially it's pumping it in circles. the only physical difference between a standard pump and a high pressure (standard body size) pump is the relief spring. if the engine is loose installing a high pressure pump will not increase the idle pressure but a high volume will. i wouldn't think a fresh build should have low oil pressure even if it's a low end rebuild.

I would just add that solving a low idle oil pressure problem with the pump requires the high volume pump. When pressure drops low enough to flicker the light, the bypass will be completly closed even with the standard spring. More pressure requires higher oil flow, thicker oil or fewer leaks (less bearing clearance). Or increase idle speed if that's possible.

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if the engine is loose installing a high pressure pump will not increase the idle pressure but a high volume will.

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Tell me you are not thinking of installing a HV pump as a band-aid for your low oil pressure? I would be investigating the cause before something goes terribly wrong. I've never had a big block mopar with less than 40 psi oil pressure at hot idle. Especially with a fresh rebuild.

I use stock type pumps on most builds now, and if you have low pressure at idle, something is damaged already or something was not spec'd-replaced correctly.

If your main bearings are full groove or 3/4 groove I have been told your oil pressure will drop off at idle. Mine idles at about 20lbs at idle and jumps up to 65lbs at 2000rpm. That's using a high pressure oil pump.

First, I'd consider testing the the actual oil pressure with a known good oil pressure gauge. Perhaps the idiot light sensor is off?