Early vs. Late 8.25” driveshaft ?’s

Your driveshaft should be fine lengthwise, my only question would be the U joint sizes.
The Dakota rear is wider, IIRC by about 2" or so... so you'll need more backspacing on your wheels. And although the spring perches may be A body spacing, be aware that if the rear is out of a 4x4 Dak the perches will be on top of the differential.