I do not see the 4x4 steering box at Rockauto. I have looked just about everywhere for one of these as I need one for my Suburban.
The only place I found that will rebuild mine is
http://www.redheadsteeringgears.com/ but they said it could take 6 months and be $1000.00
I didn't go with them because I don't want my truck to be down for 6 months. If the cost was less I would find a used core and ship it and have it rebuilt, but both the time and $$$ are a little too much for me. (But they were the only people I talked to that would even agree to rebuilt it, so I guess they can charge what they want...)
Nick