I will second the 10W30 Penn Grade oil, I build several Pontiac V8s a year for local guys and haven't had any issues with flat tappet cams since going to the Penn Grade oil. The only engine that came back with a bad cam was from a guy who changed out the Penn Grade break-in oil for Walmart brand oil he already had. The cam lasted about 50 miles!
In my opinion, from what I read, adding additive isn't always the best thing. Some say it doesn't mix right with some oils. When talking about $4000 + dollar engines, $9 a quart oil doesn't seem all that bad.
