Yes, that rumor has arisen again.
According to recent rumor, Diesel Power Magazine has the inside scoop on a diesel powered Dakota/Durango for '07 or '08. Cummins, 3.9L, V6, somewhere around 450 ft/lbs, mid20's mpg.
I've also heard of a light duty F150 offering from Ford.
Anybody read that magazine? Any insight? Can't seem to find a copy of it around here.