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Yes. Ford didn't address the issue until the 2003 model year with longer threads in the heads. Even with that the cange was not made until 11/03, so there are 2003's with short thread heads. With proper maintenance all year plugs should be fine. Don't run them for 100K miles and a periodic retorque will fend off most of the problems.
Yes. Ford didn't address the issue until the 2003 model year with longer threads in the heads.
Not entirely accurate - Ford was aware of an issue, and addressed it early on. It might have been much worse if they HADN'T done so earlier.
December 1996 - 4.6L 4V alignment feature added
February 1997 - 4.6L 2V head alignment feature added
September 2000 - WEP (Windsor Engine Plant) 2V head alignment feature modified (4.6/5.4/6.8)
November 2002 - WEP introduced long thread heads on 2V (all)
May 2003 - REP (Romeo Engine Plant) introduced long-thread heads on 4V 4.6 and 5.4
November 2003 - REP introduced long-thread heads on 2V and modified alignment feature