I need to check and do some homework.
I am looking at the 2001 service manual, and the heaviest diffs it shows that I assumed were the Dana 80's. Then dropping down a level in the manual to the next set-up they are stacked correctly. So I need to verify where the differences are for the Dana 80, modified 80, and the 70.
My truck has the 70 and I think the eth uses the modified 80 and the dually trucks use the 80.
I will check this , this weekend.