Like Chryco, I can't be certain which cam and how deep the rust is. I do know that many cam manufacturers use a surface hardening process on the cam lobes. This only hardens the wear surface of the lobe and has very little penetration. While I can't be sure the extent of rust on your cam, if it was mine, I would go ahead and swap out the cam and lifters. It would be a pain to go ahead and use that cam only to find it worn out shortly after you get it running. The failing lobe could generate small particles that would find their way throughout the engine causing greater damage. Change it out to be on the safe side. Just my humble 0.02......
