I have not read all 8 pages here. I have changed these type plugs on my '07 FX4 with 5.4-3valve ... exact same plug construction, only the heat range differed. I did it cool, used Kroil, etc ... I had 6 of the 8 come out well with patience, #2 came out leaving just the lower barrel and broken lower porcelain in the head. #8 though, the threaded body came out but it left the complete porcelain, conductor, and lower barrel stuck fast in the head.
The Lisle
65600 kit took care of #2 very easily, just follow the included instructions. #8 plug was something else, the instructions said to grab the top of the electrode and pull as you wiggle, it was in my truck and #8 was not so easy to get anything into to pull with,
so I ordered a Lisle
65710 "porcelain puller" overnighted to me. It has a 4 jaw spring steel end that snaps over the top of the electrode, it's gets used with a tube already in the kit thus locking it on. It pulled the center electrode with porcelain out, then the barrel extractor finished the job. The #2 I used the pusher to push the broken lower porcelain into the lower part of the barrel, it will not be pushed out, it gives just enough room for the barrel extractor to get a grip.
The
65600 plus the
65710 makes a
65700 kit. Might be cheaper that way. When the porcelain pusher is used, it sets a limit on how far it pushes. The kit really works. Have air and a nozzle with 1/4" ID hose for blowing out cylinders. If you put the hose into the cylinder then pull the trigger on the blow nozzle, the air going in will come back out past the hose with any porcelain particles, so wear eye protection. Really, the kit will all but guarantee no head removals.
Pictures below are same type plugs, just heat range differs.
The newer plugs have a slightly different look at lower barrel to threaded body and slightly different attachment of the ground electrode. The top of the plug also raises the seat for the coil spring thus applying more pressure in use. In this picture, the threaded seat is at the same level. You can see the change.
Anyway, doing it on my truck let me know the '08 Mustang GT will be a piece of cake.
Oh yeah, I used a smear of nickel AS on the 10mm smooth barrel extensions only.