Update........
I decided to take Hotrod Lincoln‘s advice and stay with a cork gasket. Having decided that, I wondered if my leak was due to an old, faulty gasket, or uneven edges on my valve cover? Decided to go through the process of elimination, so I started by wiping off all the oil and some debris off of the original gasket, straightened it out as best I could, and left it in place. Next, I retrieved an NOS 216 valve cover I bought years ago at a swap meet. Upon examination, the edges looked near perfect, so I installed it on top of the old gasket. Tightened the 2 acorn nuts finger tight and then about 2 more turns with the wrench. That was over a week ago, and after putting about 50 miles on the truck since then there have been no noticeable leaks. I’ve determined that the problem must have been uneven edges on the original valve cover. I’ll update again if over time it begins to leak again.
