Originally Posted by LONGBOX55
Originally Posted by GMJager
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.

Thanks for including that LONGBOX. the center section of the 55-59 will swap, and the pivot points on the axle housing would need welded up. Or as someone else mentioned... the 55.1 rear end is a complete swap in. Thats what I did.
I had to drill new holes in my spring perch pads to relocate the rear exle to the center of the wheel well

1954 Chevy 3100