You did good on the ring selection for long service and less wear on the cylinders.
The cast iron may have run in quicker but the oem went away from cast iron top and oil rings on cast iron cylinders in the early 50's.The ring manufacturers claimed 3 times the cylinder life for the chrome plated.Your Moly sets normally use a top ring with a moly filled groove which reduces wear in high heat and marginal lubrication that the top ring sees.The oil rings will have the wearing surfaces chromed.The 2nd ring is usually cast iron and plays a large part in oil control.But the package is engineered to give long life with minimal special run in required required.
Cylinder finish and cross hatch form can affect the run in needs and since the comp sealing rings are gas operated(expanded harder to the cylinder wall surface by combustion pressure
) in modern ring sets they need to be worked sufficiently hard to start this close mating of ring sealing surface to cylinder sealing surface.
So: avoud short trips, make it run near 200 deg temp, no oil additives during run in, basic oils only and as light as you can be comfortable with, make it work as hard as possible(combustion temps and pressures are up with larger throttle openings/heavier loads).
War story: we rebuilt a 6v53 Detroit used in the upper on a P&H crane to lessen the oil leaks and consumption using all GM cylinder kits so the finish and material was proper.When put back in service the leaks were cured but the oil consumption was much higher than before the rebuild.We put up with this for approx 6 months and saw no improvement so pulled the engine out and sent it to the manufacturers shop where it got I think 2 hours on the dyno at increasing loads.After reinstalling the engine now had an oil appetite like a good engine.The upper engine in a crane sees long periods of idling and is usually running a bunch of pumps which are not heavily taxing on engine output most of the time.
Run it hot and hard and ask your head builder what guide seals he installed.Some don't install wiper type seals on the premise that the guides are not properly lubed but the factory has used them for quite a while now and these modern OHC engines would not be acceptable without good oil control at the stem/guide.
