Me thinks your confusing the Dana 60-2(they have the 60-2 cast into the housing above the pinion shaft ) 4x4 front ends with the Dana 70, some of the later 3500 CTD trucks came with some version of Dana 70 up front and Dana 80 in the back
I'm going to do some research on those 61 carriers to see if they will accept the Dana 60 35 spline clutch type posi internals