Went with a 12 bolt posi from a 78 chev suburban 4x4 in my 54 3100. Its a little wider but fits nice. I have 3.07 ratio but would rather have 3.55 or 3.73. Mods needed for mounting to springs to get centering right. And of course trans upgrade to facilitate open drivevshaft. Its been in 23years and im happy.
