I was going to leave it stock...

Rotella T 15-40. Used it for years in fleet service. Had a bunch of Mack trucks.Also used the same oil in all of the company cars and gasoline trucks.If I add it all up,millions of miles.Only had 1 cam go flat in a 305 Chevy engine at 150,000 miles.The engine was remarkable clean inside.
Now that said, I know the government had made oil companies change there zinc/phosphorus amounts in the last few years.I do believe it to be a good oil.
I have also heard that the oils are ok AFTER break in.I do use Lucas break in additive during first run rebuilds.