21A rods set up on a 4" Merc crank

[3W Hank]

On oil clearance by using the 21A rods.
I has a baby stroked 4” crank done in LA back in the days, and it's Ok on them mains but
need a undercut on the rods.
I has a set of NOS 21 A rods and sets of new but old bearings.
But how to set-up clearance on this design ( full float ) I has Berco crank grinder so I do it myself.
How is one set-up diameter in the rods, and how to measure clearance with bearings like this ( never been into it before )

Then on oil, by using the full float, what oil do they like, I has a new NOS 8BA pump ( maybe wrong or not needed as to 'much' pressuare ) and a truck oil pan I will make a screen and a scraper inside.

This is not a street rod engine, but not full race.
But for streets, but minimal use ( but like rew up )