If you feel like reading, this is an article I read in Hot Rod and have used many times when these discussions come up. The article explaines everything you need to know about why you need to select the right oil. It would be a shame to wipe the lobes off your cam!
http://www.hotrod.com/techarticles/engine/flat_tappet_cam_tech/index.htmlHughes Engines has a good piece on this subject as well.
http://www.hughesengines.com/general/techArticleDetail.asp?articleID=1000039It is worth a read too.
Long story short: There is a star burst insignia/seal thing on the oil bottle. If it says "specially formulated for gasoline engines" or "newer cars" or "energy conserving" stay away from it. Also on the seal it will have the API rating, SH, SJ, SL, and especially SM is bad. Those rated oils have the least amount of ZDDP (the zinc) in them.
The oils that say for diesels, off-road use, or the 4X4 oils are pretty good. The best would be Royal Purple or something like that.
Goody, I hope your daily driver is a roller lifter motor or you don't care about cam wear. Castrol GTX has an API rating of SM, the worst rating. I have a bottle here, it says "Unique Anti-Sludge Formula". That would translate into "We took all the good stuff out."