340 oil pump

If you are generating 50 psi with the stock pump then stick with the stock pump. A pump just moves fluid, what creates pressure is a restriction in flow. If you have a "tight" motor your pressure will go up until you reach the relief valve setting, in this case 50psi. If you have a "loose" motor you may not be able to get to your relief setting because the oil is bleeding off past the clearances almost as fast as you can pump the oil. In other words the volume of the bleeding off matches the volume of the pump. In this case you need a higher volume pump to overcome the clearances so now your pressure goes up.
So if you are running a HV pump with a "tight" motor you will never run your pan dry because all you are doing is putting the oil back into your pan thru the pessure relief valve in the pump. So this is just wasted motion. What is the advantage of running something bigger than you need and wasting the overage buy putting right back were you got it? Running a HV pump also puts more load on your pump drive gear. More load = less horsepower. I run a stock pump in my 340 drag car that runs low 11's and my oil pressure is just fine, it is 70 psi at 7000 and 20 at idle hot. It's just a matter of matching clearances to pump volume. HV pump came around in the 60's and 70's with the advent of very loose clearance race motors. the only way for these motors to build pressure was to run a big pump. Now we have gone the way of tight clearances and smaller pumps and thinner oil. Ever notice how some modern motors use 5w-20 oil? it's because of tighter clearances.
Just to clarify one thing you can't compress a fluid.
I also run my drag cars one quart low so I don't whip up the oil from the windage of the crank spinning. Introducing air into your oil or any hydraulic system is very bad.