I have driven 75-79 full time 4wd Dodges forever, and never had a single wheel bearing issue. The bearing setup is like an early version of the wheel bearing that almost every vehicle has been using for 25 years. In fact, having the grease fitting makes them better than the 94 and
newer trucks in my opinion.
If one was to install a part time transfer case, and leave the full time front axle, you would have almost the equivelant of the 94 and newer trucks and maybe gain a bit of fuel mileage.