I thought some 70 spindles were the same as 60's?
So many variations of both 60 and 70, SRW and DRW... I don't think you can say a 70 shaft will fit, or not fit.
Search Dana 60 bible to see exact specs of what you have, length, diameter, spline count, coarse or not, bearing sizes, etc... Then cross reference that into the Dana 70 bible
After all this work, you'll most like explode that tiny little 5:38 pinion before anything else