There has to be a reason that someone took it all apart. Perhaps one was bad and this is a replacement. It's likely impossible
to know unless the previous owner said something. I would check it out and see if there is some obvious problem with it.
Possibly take to a shop that works on differentials to check it out. It's a lot of work to install it and the axles and then find
out it has a problem and have to do it all over again,
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine