I use some break-in lube on the camshaft and then run Shell Rotella 15w 40 diesel oil, for muscle car engines. The diesel oil has ZDP additives still in it. They just changed the formulation, but I called Shell and it still has enough ZDP for flat tappet cams. Rotella is reasonably priced, and available everywhere. The specialty oils are great, but cost more, and what do you do if you need a quart out on the road? The other issue is be careful adding to much ZDP because it can actually cause issues it you add too much. Say a specialty oil and additive on top of it.
https://www.hemmings.com/blog/2012/10/18/tech-101-zinc-in-oil-and-its-effects-on-older-engines/