IIRC Takeda did a good write-up of the spark plug system on the 3.0 a while back.
The factory plugs are plats on the center electrode on one side of the engine, while the opposite side has the plat coating on the ground electrode.
One side fires the spark from the center to ground , the other side fires from ground to the center.
When replacing the factory plugs you must get double platinum plugs (preferably fine wire) for the best performance and longevity.
Many on here have found problems with plugs other than Motorcraft/Autolite , such as Bosch in less than 20K miles.
Archimedes screwed us !
I knew a blonde dyslexic agnostic insomniac - she'd lay awake at night, wondering if there really was a Dog.
2003 Ranger Edge 3.0 manual 2WD