Dana 60 & 80
You can use any GL-5 rated gear oil. However select the appropriate viscosity for the ambient temperatures the vehicle will be operated in. I. E. Above 90 degree F use a GL-5 with a viscosity of 140, if operated in temperatures above -10 degrees F use 90, 80W-90, 80W-140, 85W-140, if operated in temperatures below -10 degrees F use 75W, 80W, 75W-90, 80W-140. Many choices, I use a synthetic 85W-140 in my 99 Ram 2500, it also has the Dana 60 and 80.
Jerry