I don't believe that Ansmann ever sold the conversion kit from X2 to X2C. They only sold the kits.
The team C conversions can be found here:
For the Saddle pack chassis :
http://www.teamcracing.net/index.php...mart&Itemid=71
For the stick pack chassis:
http://www.teamcracing.net/index.php...mart&Itemid=71
Either of these it might possible to order from SMD