I think the trick is to keep it close to the original, but not to follow the originality exactly. You don't want to lose the essence of the car.
For instance, our E-type has minilites (replicas), the engine big bore head and six branch manifold, the interior has some bucket seats and a smaller steering wheel. The later two are probably the most off topic (
), but make it better to drive (for us). It was always your bum that slipped first when cornering!