That is one of Mike's center diff units yeah, but we've all been waiting a long time for him to start selling them properly in the RCM shop; at present its a custom order thing only. The other CDs fit inside the transmission, and that way you can fine tune the gearing but more accurately with the spur and pinion. Just stick some ~500k fluid in the CD and that should be a good start for the traxxas version.
You wont use your slipper with the internal CD, but with Mike's unit I believe you can use his slipperential to help tame wheelies too:
http://www.rc-monster.com/proddetail...Mslipperential