I read some threads a couple of years back when I needed to change my original ATF on the 01. 5. I just put in Dexron III with one quart of 5W-30 SYNTHETIC motor oil per change. The truck has over 100,000 miles on it and is doing fine. I tow 8,000 lbs of travel trailer through the mountains of Mexico and up to Illinois and back a couple of times a year. I change the ATF often, about every 15,000-20,000 miles... it always looks fine, but it is cheap insurance against a failure.
Steve