Here we go....
I use 10-40 or 20-50 Kendall or Lucas "Hot Rod & Classic car" Oil.
These both contain lots of zinc and are formulated for these old engines.
I would NOT use any of the modern, very thin synthetic oils.
Please understand, THIS IS JUST MY OPINION.
I am sure others will have different thoughts.
This works for me.
Other oils may work for others.
Chris W.