What's the best oils for tappet cam engines?

I have to agree with Rat Rod on this one. Once you break in the cam properly with the Zinc oil go ahead and use your favorite; I use synthetic. That's what I did for my 360 in my Dart when I built it 7 years ago and it's been great ever since. I just purchased a new flat mechanical cam from Lunati for the rebuild on my 360 in the Dart and that is what they say to do. Highly recommended from every cam manufacturer I've spoke with is to take out the inner springs when breaking the cam in and put them back after. This is to make sure that lifter spins and properly seats to the lobe. As for synthetic I have found a private label synthetic from NAPA that I have used for a couple of years that is working great on my Dart and it's so much cheaper than any other synthetic. I use the 15-50.