Two possibilities if certification is required
A US type STC. For stuff like crankshafts or valves I suspect this would essentially involve a recertification test (the 150hr? one) for the new components.
A new! engine the Deaf V1670 with eg Packard crankcase and heads, RR gearcase with new pistons, crankshaft, valves, gears etc Modern fuel injection and ignition.
All it takes is money for development.
The engineering shouldn't be too difficult if the market is there, as an example look at VW's where you can build a complete motor from 3rd party parts which are often much improved from the original. We can assume that the materials have been improved considerably, even in cases where they are nominaly the same the nasties (eg P and S in steel) have been cut back and processes such as vacuum refining can help consistancy. Having said that there could still be surprise problems as shown recently with Lycoming crankshafts.
One point that should be noted is that with piston engines the development often has to be done with the whole engine while with turbines things like the compressor, combustion chambers and turbines can be developed separately in test rigs.