I wondered about reground too and how they would maintain lift spec. In an episode of "How It's Made" they showed cams being done at a rebuilding facility. If they are all treated like those on the show, the old cams were ground down slightly more to prepare the surface and then had metal added back via an automated welding or another process. They were then placed in a machine and the excess reground off. They then had some kind of metal re-strengthening and finishing. The announcer said the cams were either returned to factory spec or could be modified to different specs depending on the desired use.