which gaskets are best to use with o-ringed heads? I have read that black diamonds are best and I have read oem is best and have also read that felpro was best! Don’t know what to believe, anyone have any experience with it?

In any service situation, including DIY, experience will be the tell of a best product. And that also can be influenced by the installation technique. When I talked to FelPro they did not endorse their gaskets with o-ringed heads, but how could anyone expect them to. There’s no standard for the o-ring groove or wire, so it's placement may vary to the fire ring design of the gasket maker. IMO the best answer you're going to get is from the supplier of the head, who should be testing the fitment.

Again, IMO, I believe most of the re-gasket failures are due to prep and inspection, and a suspicion there were early design faults with the heads themselves and possibly corrected with the latter production 20mm heads. All based on armchair experience.

This took awhile to sink in. Was this a Ford remanufactured motor?