Sorry for the late reply, did you land anything? I have seen 87-90 Dak rears on car-part.com for a few hundred bucks. Look for the 90 Sport, a lot of them came with 3.90 sure grip stock. I have a complete truck with one. Another alternative is a E body 8 3/4. Within 1/4 width of a gen 1 Dakota rear. As far as gears, I havent tried myself but have been told that YJ, TJ and Cherokee gears will work. There was an axle spline count break but am not sure of the year. If that holds true, I know they made gears all the way down to 4.56 for the Jeep 8 1/4.