repro parts

I try to keep engines the way they are found, but when repro parts are added is there a way to counterfeit their newness?

Depends on the items and texture you seek to reproduce. Pitted cast iron is best reproduced with a sharp wide punch tip to simulate the deeper pits, and a rounder narrow tip for shallower, and then 60 or even 40 grit blasitng sand (aluminum oxide works best) at lower pressures with a pressure pot system (sometimes higher pressures if the cast is high in carbon nodules), or regular pressures in a hopper type.

It takes some patience, and a little self taught skill to get things looking right.