Hi Guys, I've benefited from many threads here and just giving a little back about my spark plug change experience on my '09 ex-Police Charger...
I've owned the car about one year and had only recently had a chance to change the plugs. I suspected they'd never been changed and discovered I was right. I pulled the original plugs out with over 107,000 miles on them and the car's been running great for me this past year. Gaps on the OE plugs were on average about 0.055". They didn't look much different from other used plugs pulled from 5.7's posted on this forum (other than big gaps).
I put in Champion 9055 Iridium plugs, purchased from Rock Auto for $5.56 each.
Job took less than 90 minutes and below is a photo of the tools I used. The Mac Tools spark plug install tool does speed things up without worry of cross tread as it's just rubber, has enough grip to spin the plugs as long as there's not much friction, meaning if you're cross threading the tool will loosen on the plug.
That's a 1/4" drive speed wrench, 6" long 1/4" drive extension and u-joint all for coil pack r&r. I did need the longer lever arm of the 3/8" drive socket wrench to remove such old plugs and was nervous with each tug as it made the typical dry thread screech I was saying prayers for a clean removal (and was granted!). I did not use a u-joint for actual plug r&r, just different length extensions on the plugs close to the firewall.