The cam will be experiencing a "metal to metal" forced contact every time it rubs across the lifter. There may also be a "hammering" action where the metal cam may actually have a "plastic" tendency.
You can take a big sheet of 1/2" float glass and tilt it up on it's edge. After a while the bottom will measure more than 1/2". I'm not sure about the hammering action on a cam, and whether it's enough to cause any deformity, but here's what I would do.
I would go for the oil product best known for minimal wear, and I'd be sure I didn't get "any" rubbing action out of the cam. From where I sit, Amsoil Series 2000 Racing oil has the absolute BEST anti wear specs in the business. I know of no product at any price that can beat it. Here is a link to the 20W50 I've used in my 928 Porsche. http://www.amsoil.com/products/tro.html
Here is what I'm talking about regarding the wear spec.
They have a 0W30 on the market, but I would also look at the 20W50, especially in a big block where the tolerances might be larger than some of these small imported mills.