Theres lots of contradicting info when it comes to oilpumps and engines with mileage on them.
Usually you can adjust the thickness of the oil to make up for the loss in pressure due to the extra clearances and adjust the operating temps say going fron a 180 degree thermostat to a 170 degree thermostat.
High volume pumps deliver a mere 15-20% extra oil and when you have an engine thats running 5-10lbs hot at idle that 15-20% extra pressure can help prolong the life of the engine.
When you rebuild an engine its very important to know bearing clearances for the whole rotating assembly as the rod,main camshaft bearing aswell as lifter bore clearances dictates the viscosity of oil and whether a HV oilpump is warranted from the getgo.
Lots of experts in the field say if the crank is running stock bearings everywhere with stock or slightly tighter than stock tolerances a regular oilpump will suffice but in a fresh rebuild with a crank thats undercut say .010" with a couple extra thousandths in the lifter bores that adds to excessive bleed off and in this case Id use a HV oilpump and not drive it so hard...
Another instance is in my newest 410 stroker build...Same brutal torque build-up as the 408 and seeings I hate using roller camshafts even though they alleviate friction in the upper valvetrain they are also prone to failures due to quality control issues concerning roller lifters and lifter bars not doing their job on everyday street driven vehicles with non-roller blocks so instead I went with a set of EDM style extra oiling lifters that have a tiny hole lasered into the bottom centers of the lifters to force oil between the flat tappet hydraulic lifter and the camshaft lobe essentially alleviating rotating friction in the valvetrain aswell but those type of lifters will also tax a stock oilpump so in this case a HV/ High pressure pump is warranted and to do the job Im using one from Milodon in my 8qt Canton oilpan w/crank scraper and slosh baffle to control windage and oil return back to the pickup..
I'm also making up for the friction of a hydraulic flattappet camshaft by using a set of shaft mounted roller rockers.............On the 408w I ram Comp Cams pro Magnum Steel full roller rockers w/7/16" studs and stud girdle but they were a tad too noisy for my liking after a 40-45 mile run...
Im even running Edelbrock E-Street heads with the smaller valves yet on a carb on a dyno first pull the flat tappet hydraulic .477/.493" lift camshaft made this kind of power after breaking in the camshaft...Then with my EFI Performer intake that according to Edelbrock delivers an extra 40ftlbs more torque with my performance tune it was closer to an extra 60ftlbs more and the brutal torque came on a lil earlier too............LOL
I plan on breaking the 410w in on Driven 5w/30 conventional break-in oil with ZDDP additive and running it on 5w/20 Amsoil after break-in to keep the distributor gear from prematurely wearing from excessive pressure then as engine wears and pressure starts to drop simply adjust oil viscosity.....
But in the end of my speil like I stated there are reasons and rules to the exceptions...
Another exception to the stock bearing stock clearance stock pump rule is if youre using an oil cooler youll need a high volume/high pressure oil pump aswell..