If a 'restoration engine' is a polite way of saying restamp, aside from being accepted at judging, it seems the reality is it's really no different than a 'numbers matching' engine but more refined and actually a perfect forgery in all respects other than being admitted as such?.
What seems to suck w/ terms like these is you need to be part of the in-crowd to share in known history of specific cars to remove these kind of clouds (that have intentionally been put in place) to learn/know the truth?.
Restamps are restamps no matter what they're termed (factory correct in appearance or not) and no matter what many like to say, how can the values of some genuine cars not be be lost/watered down when these above practices are acceptable?.
What sucks too is regardless of how other GM models are currently restored/judged, it seems much of the Corvette world's judging direction and restoration techniques eventually filters down to other GM models and other makes later too..
~ Pete