Check all vacuum lines for the EGR system. On occasion, they can nice and toasty warm, and melt......

No EGR would give you some spark knock..... Might be the passages in the manifold are getting clogged as well.

 

3924 is stock heat range. 3923 is one heat range lower. My truck hated Autolites. They come with Champion so maybe throw a set in there one range cooler than what's on the radiator support. Always regular copper in these. My truck also pinged until about 110k miles. Run higher octane and drive it hard. It may just have one hot spot in one cylinder as many have reported. The #8 cylinder has been a culprit of many ping stories. Also heads may be to blame, but don't cross that bridge yet.

Here's some good reading. The Truck plugs are no longer made.
http://dodgeram.org/tech/gas/spark_p...park_plugs.htm

Also check the wire routing per this TSB:
http://dodgeram.info/tsb/1998/18-48-98.htm

 

Just a long shot here, but I thought I had a ping issue in the last few weeks as well. Was driving me crazy.... turned out to be u joints...swear to God they sounded exactly like detonation and only when under load...never heard a ujoint sound like that in my life... it's worth checking. Also, I had no slop in the joints when I checked them. I only figured out when I was pulling along side a building and I could hear the slightest noise from them...