[tomk]

from http://Dodgeram.info/Engine-Gas/SparkPlugs/sparkplugsEricP.htm:

The 522? series is similar to the 392?, but has a longer 'projected nose' than the 392? design that puts the spark farther down in the chamber, which has an effect similar to slightly advancing the ignition timing 2-3 degrees. Note this timing effect might increase pinging if timing/carbon deposits are at 'the edge.'

Many 5.2/5.9s are on (or over) the edge into pinging, so the 329x plugs often work out better.