I'm using the Brad Penn 20W-50, which is like the old-school Kendall, with old-school additives. The subject of appropriate additives for older engines has been beat to death on the Internet, so I will leave it to you to do your own Google search. I'm not sure whether the additives package matters as much in our Alfas as in some other flat tappet engines, e.g., American V8's. If you are using the correct valve springs (not the Jaguar ones that are often used) then the low pressure on the cam lobes might make this a non-issue. Also, the metallurgy on the 750 cams seems to be different from later camshafts, which may be a factor. (Steel on 750, cast iron on later cars.)
At least the Brad Penn makes me feel good.
I'm no tribologist, I just read too much stuff on the Internet.
The perfect is the enemy of the good. Voltaire