Another issue with HV pumps in a Windsor is the hex-shaft that runs the pump from the distributor. Heavy oil and an HV pump has been known to twist and sometimes break the hex-shaft.
I've got a little HV oil pump story:
A good friend of mine had a very high mileage (~400,000Km) 302 in his Mustang. The engine had an unknown history and had seen a lot of passes on Nitrous, as well as numerous nitrous back-fires.
The engine didn't have very good oil pressure; 12lbs IIRC with the stock pump in it at idle with 20w50 in the pan. So, he swapped in a Melling HV pump. His oil pressure got better (around 20lbs) with the same weight of oil and he continued to use the car.
One day at the track, I broke my tranny, and he had a Nitrous "issue" which involved a mouse eating his injector harness, causing an intermittent injector, and subsequently a melted plug and burnt valve.
He was running stock heads, and I had mine sitting around, and so instead of fixing his head, we just swapped it out with one of mine. The head from my engine was MUCH cleaner than his and he made a remark about this after we put it back together.
Even though it ran fine, from the pressure issue the engine had, we knew the bottom-end wasn't overly healthy. That fall, we pulled the engine out of his car and tore into it.
ALL the rod bearings showed copper. A LOT of it. As did all the main bearings. Yet with the HV pump, it had around 15-20psi hot at idle even after the most recent incident.
So yeah, the HV pump made what he saw on the gauge look better. But it didn't change the fact that the bottom-end of that engine was very worn and needed attention.