Break in oils, zinc and all that jazz

This is the first I've heard of a zinc issue with oil. Someone else mentioned zinc on 'another' forum, and when I asked, nobody responded. So - is there a particular type of oil we should use in our old flat-tappet hydraulic cam engines? What do I look for when I go to Napa auto parts? Also, what's the recommended oil weight for a V8 (recently rebuilt) with old technology?