Tom,
I wouldnt expect a DER to know about the inteaction of valve tip and rocker materials, would you? And the difficulty is also relative to the type of engine. An A-65 or Franklin should be a lot more straigntforward than a TC Wright engine. Dont get me wrong, I love making parts for old engines, however I have seen a lot of poorly made parts that were due to the individuals lack of understanding and knowledge about the part they were trying to duplicate. Take a crankshaft for instance. Sure you can measure it for dimensions, thats simple, materials can be scanned with a GS or an SEM ( both is better ), thermal metal treatments can be estimated. However what about mechanical treatments like shot peening? What size was the shot? What pressure? What angle? How long? How many times? This is where you would make multiple parts, and try various types of shot peening, cut up the cranks and compare them to a cut up original. Under the eye of an expert metalurgist this would still only give you a "best guess". This project undertaken by a group of people experienced in crankshaft design would at least have a decent chance of working. Done by anyone else would be a risky business. So what does this come down to? It aint gonna be cheap!