RE: 2001 durango misfire
Exactly, Plats are a no go on our Magnums. That is probably your entire problem.
On your 4.7l, go back in with OEMs or NGKs.
For 5.9l's reading this thread, Plats are a no go for you too. Go back in with OEM (great lifespan, pinging however) of move over the the AutoLite 3923s. No book will tell you to use 3923s, only other expert and knowledgabe Durango owners. Ask for then by name, not cross-referenced for your 5.9l