2003 5.4 Denso coils p/n 6736000
I recently changed out all eight on a newly-acquired 2003 with the 5.4. Vehicle had 155k on the odo, so who knows if they were ever changed. They weren't giving me any problems, but I'm going to be using this vehicle for road trips, so I don't want to be stranded somewhere. I guess it was cheap insurance for me is what I'm trying to say.
Anyway, I installed the Denso coils (p/n 673600, but I think these only fit 03-04 for 2nd gen. Check before buying.) I paid a total of like $190 shipped for all eight from rockauto.com. They seem to be working fine. I've put about 2000 miles or so on the vehicle since they were installed. Bonus, they're made in the USA!
Also, I installed Autolite iridium plugs. Made in Mexico. Not as bad a China, I guess.
Hope this helps.