Here is an article from Hemmings that discusses the ZDDP as it applies to older car engines.  Most of the information applies to our flat tappet (rocker) engine in the Savage.....however we also have to consider the wet clutch and avoid any oils with "Friction Modifiers".

http://blog.hemmings.com/index.php/2012/10/18/tech-101-zinc-in-oil-and-its-ef...

The one thing I found interesting is that the article claims the ZDDP benefit occurs during the engine starting period....when the cam and rockers are not bathed in a coating of oil (dry start).  This is the first time I have ever heard that ZDDP functions to protect the cam and rockers during the starting period.  I had always assumed the benefit occurred continually.

Whenever the benefit occurs.....I do believe that a 1,200 - 1,400 ppm ZDDP content is needed for the Savage engine.  Below is a photo of a cam from a bike with 17,000 miles on it that was obviously using an oil that did not have enough ZDDP.  The bearing surfaces are in good shape which shows the engine was getting plenty of oil - but the cam lobes and rockers were suffering from inadequate protection.

I have seen the identical spalling on Lycoming camshafts.  Generally it is from the engine getting infrequent use.   If they sit for a few months, and there is any amount of condensation in the engine, tiny little rust spots start on the cam lobes.  

After a while they actually spall and pit like that.