I don't think there are any rebuild kits for the Sporty's diffs. But there aren't many parts to swap out. I have my new 5.38 R&P sets installed and they are working great. I did have to readjust my speed calibrating box because the speedo was reading 5 mph faster than I was actually traveling, based on my GPS speedo. Here's a link to my build thread on the 5.38 R&P upgrade.

In a nutshell, you will need for each differential...
2 carrier side bearings
inner and outer pinion bearings (1 of each)
gear marking compound (can be purchased for a few bucks on Amazon or eBay - one vial will last forever!!!)
1 new crush sleeve OR 1 solid pinion spacer - I highly-recommend the solid spacer! I had one custom-made by Spence Weir at http://www.weirperformance.com/solidpinionspacerkits.html.
1 new pinion seal

Those are the only major parts to be replaced, assuming you want to replace all of the bearings while you have the chance. My build thread will get into the details of how I did it, along with the info on parts and part numbers. Hope that helps...

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