When I had my 80 I didn't need a CV rear driveshaft only because it was a longbed when I did the the swap for the trans, I also swapped in a 22r. If it were a shortbed it will need a CV rear, also make sure that the rear axle pinion is pointed at the tailend of the transfer case or it will cause a severe vibration. When I had put the duals in my current 4Runner it required a CV driveshaft to eliminate vibration and help with travel since it will bind at the u-joints with the shorter driveshaft in the rear.