This is a picture of the pivot areas that need welded up on both sides of the rearend.Be sure to remove as much of the rubber grommets as possible,it will burn and drip out on you.Make sure you set the pivot angle of the rearend before welding.
use 1955 to 1962 1/2 ton truck 3rd member.
I used a 3rd member of a 1958 1/2 ton truck 3:90 gears in my 1951 suburban.
Do a search on the subject,there is plenty to read.
pivot areas Good luck,
Tim