Oil In My Spark Plug Threads On A 302

[MustangMando]

Took out spark plugs after 100 miles of usage and noticed oil on the threads. I bought this car a few years ago and never drove it, since i was restoring it. Took it out for a drive a few times and decided to look at the plugs since the car was running rich. All plugs were black and had oil on the threads and maybe inside. Had all gaskets replaced for this car about two years ago. And engine has a tick like it is a lifter, thanks for any info.