[flatheadmurre]

Right thing in the right place...do you need the bearing clearance...then you need a highflow pump.
If you don´t need the clearance you only gain heat and perhaps bearing cavitation trying to push a lot of flow through a narrow space.
So why do you need larger bearing clearance...when you start pushing an engine to the limit metal flex.
Oil has a limitation in load...no one would use a 70W oil in an engine if they didn´t need it for a reason...you don´t need the heavy oil to deal with force...you have everything to win with a lighter oil and tighter bearing clearances.
An engine that has been linebored dead on...crank that has been ground and micropolished...good synthetic oil...you can go down to .00075 in clearance.... a normal setup needs .001 clearance for every inch of bearing diameter as rule of thumb.
Tighter bearing specs distribute load better giving less friction combined with a thin oil taking less power to pump.
A race engine is basicly "worn out" from start in the bearings to be able to deal with force and heat.