Stainless, Bushed PRW Rocker Arms

This is not correct. Bronze alloys are homogeneous in cross section when drawn, just like steel. Oilite is a commercial brand of a type of bronze that is recast with a special process that creates pockets throughout the material that hold oil. It looks a bit like a bronze sponge if examined under magnification. There are many alloys of bronze and some are very hard and tough, approaching mild steel. Oilite is weak in comparison and usually used in applications where the oil supply is limited and not continuous, such as on an electrical motor or all the shafts on my Sioux valve grinder. Because of it's porous and not a solid material, Oilite cannot carry the loads that regular bronze can and would never be used for a rocker bushing or highly stressed component like a main bearing or punch press slide.
Ampco 21 is way harder than mild steel not to mention it resists abrasion and cutting with cutting tools like a lathe bit.