They can regrind the old cam just fine. They can manipulate the lobe anywhere on the cam core they want. They do that by moving the base circle. Mopars normally require a longer pushrod to make up for that difference. No big deal as pushrods are pretty cheap. I also agree with using the old cam core. According to Ken at Oregon, they are hardened pretty much all the way to the core. I'm not sure a new one would be hardened that deep.
