No one here will be able to just spit out an
oil or viscosity without knowing how the engine was setup. Call/email Blair and ask him what he wants you to run.
Just as an aside, most "good" hydraulic roller lifters will not run on 40-50W on the hot side of the viscosity. I know you have solid roller lifters, but just saying this for the benefit of everyone else. A Morel lifter, for instance, will poop its pants trying to run with thicker
oil like that.