Nippondenso stock in a Duratec? Wouldn't Motorcraft be stock?
amc, patience - when I get around to replacing the mounts when it stops raining I'll disassemble the bad mount that is on the car and replace that video with a longer one with the disassembled mount. I had the opportunity to get both mounts side by side and had 45 minutes to shoot that, before the Anchor one had to go back to the auto parts store.
My goal with that mount business is to try to get a complete video Expose' posted on the differences, but I don't have the time or money to go searching wrecking yards looking for a blown-up Anchor mount or buying a brand new one and destroying it. If you happen to have a broken one let me know and I'll paypal you shipping so I can take it apart.
Anyway, I didn't mean to hijack the thread on that.
one last thing to the OP on this loosen spark plug business - by any chance are you seeping coolant? The reason why is that if your cooling system is not pressurizing then you may have coolant boiling in the head - resulting in localized overheating of the head - that might be responsible for the plugs getting loose - it's a long shot, though, just a thought - personally I suspect all the threads in the head are thrashed.
If I was in your shoes, and even after following all tips they were still coming loose, I would JB Weld them - recognizing of course that this was a truly last ditch attempt before pulling the head. I also wouldn't drive the car outside of the extended towing range for free AAA towing. :-).
If a plug does blow and carry the threads with it, JB Weld is no longer an option.