the 55-59 should be bolt in swap (other that switching to open drive). Someone will correct me if I am wrong though
That is correct, but you would not necessarily have to swap the entire rear, only the third member would be needed to get open drive and 3.90 gears. The pivots would need to welded up as well. Coupled with an overdrive transmission, the 3.90 gear is a great all around ratio.
