This guy will sell these HV pump kits for $15 shipped. He's got clean ones. Tell him to send you a good one if it comes to you needing one. https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/182905028257
I wouldn't run the high volume pump unless it was the last resort. What oil are you running, weight wise? It is never a bad idea to rebuild the pump and put a booster plate in while redoing it. It is cheap insurance for an hour's work. With the oil pressure not coming up much at higher RPM than idle, I'd check the gauge. Grounding at the block should swing one way all the way. Is the gauge and the sender a matched set? Is there any chance the gauge is getting a variable ground through your dimmer dial? When I had a bad ground in my cluster, mine would raise the temp 1/4 of the sweep and the oil pressure would drop 1/4 of the sweep. Freaked me out the first time I looked down and saw it way hot and no oil pressure! Regrounding cured it.
Running Joe Gibbs Driven 10/30 just changed it a week ago. I'm not grounded at the block, I'm grounded at the dash. All grounds going to the same spot that share a ground that was already there by the ash tray. I tested for ground before I installed the gauges, unless something happened after that, I didn't check after. Gauge and senders are all custom matched sets from Speed Hut. Water: https://www.speedhut.com/gauge/GL-WTR-01/7/Water-Temp-Gauge-120-260F Oil: https://www.speedhut.com/gauge/GL-OIL-01/7/Oil-Pressure-Gauge-0-100psi Volt: https://www.speedhut.com/gauge/GL-VOLT-01/7/Volt-Gauge-0-18V
All good but I'm saying that as a test, disconnect the wire at the block sending unit and ground it. The gauge should peg one way and disconnected completely should peg the other way. On oil, you could try adding one quart of 20W50 on the next oil change to see if that improves it if all the gauges check out good. Just make sure that turning on the gauge lights doesn't change the readings.
They look close to me. If your main & rod clearances are on the large side plus running thin weight oil, the HV gears may be your huckleberry.
I'm pretty sure I found the problem... http://www.v8buick.com/index.php?threads/sunday-was-bad-news-im-going-to-need-some-help.335719/
