One tidbit i remember is that the 8.4 compression ration 8L iron V10 in high GCWR HD Ram pickups had its own Champion heat range 9 sparkplug, whereas the 5.2/5.9 V8s had Champion heat range 14 plugs.

I called the Champion sparkplug 800 number on a whim and asked why this was, and was told

"The 5.2/5.9 Magnum V8s need heat range 9 too,
But the lower GCWR half ton pickups have to meet tighter EPA emission controls,
so they have to have a heat range 14 Champion spark plug
so that they will miss fire less on a totally cold startup
and have less HC and CO emissions
in the first three minutes of running at less than full operating temperature"