B-body rear diff measurements

[xx88man]

I am going to check out an 8 3/4 rear that he says is 44" from center of perch to center of perch. He says it is from a pre-71 B-body. It is missing one axle and will need a rebuild. What should I look for besides the measurements? What are these old diffs worth?

[MoparLeo]

My preference would be #1 -742  #2 - 489 Here are the housing and perch specs.
http://www.mymopar.com/index.php?pid=73
http://www.mymopar.com/index.php?pid=62

[HP2]

Uhhh slight issue with those links, while 62-71 b body spring perch dimension is correct, there actually are different flange to flange measurements for different sets of years.

[xx88man]

Do the really early ones have keyed axles that a person should stay away from?
Is it typical to replace the axles when rebuilding these?

[HP2]

Its the 62-65 units that have the keyed axles its. easy to tell as there is a big castle nut on the axle flange.  Also, flange to flange width groups for  B bodies prior to 71 are 62-65, 66-67, and 68-70.  The year of the housing you chose, will dictate the wheel offset you need for a conversion. One isn't better than the other dimension wise.

Unless you have keyed axles, the axles are obviously damaged, twisted, or missing, you shouldn't need to replace the axles for a street car. If you are putting down big power, ever using slicks, or doing high rpm drag launches, then you might want to consider aftermarket.

Empty housings without third members or axles seem to be worth around $100 +/- some.  Complete but needing bearings and seals maybe $3-400. Bolt in units $600+ depending on if they are simply used, partially refurbed, or completely rebuilt. If they are roached out, rusted or missing parts they are worth less.

[xx88man]