Hi, I don't know if you've done this yet, but i had a stripped thread in my 2.3 too. I fixed it by buying a thread replacement kit, it is not helicoil but a steel insert with a larger thread in the outside and a spark plug thread inside, the kit came with a tap/drill. I did it with the head in the car, first I pulled out the helicoil, as someone had tried that before, then I covered the drill/tap tool in grease (to stop swarf dropping in the cylinder) then manually rotated the tool in to the head slowly ensuring it followed the old hole, I withdrew the tool every couple of turns and cleaned off the swarf applied more grease and continued until it was all the way through. I then degreased the hole and applied the locktite type compound supplied in the kit and screwed in the thread adapter using a spark plug as the insert tool (I used copper coat on the spark plug threads to ensure they would not seize in future. Job done! That was a year ago and no problems so far, besides Ford quoted me