Have a look at this...all i use is Penzoil 5w30.A lot of guys think the zinc thing is a billion dollar money maker. I think regular oils still have 800 ppm.
A few years back, I called Valvoline myself. They said "if you have a classic with 60k miles on it already, per say, regular motor oil should be sufficient". Probably true, but when we add valve spring pressure to match our cams, the care of the lubrication for the FT cam lobes intensifies.
My opinion, if your stock 318 in your '78 Dodge truck, per say, has 112k and running good, probably nothing to worry about. Once you add high pressure valve springs to match that fast-ramp cam, even a mild cam, you better be protecting your investment.