In order to upgrade to the 2.0 rear end it will be about $140 (for the conversion kit). Now to get the 2.1 parts it will be about another $100 I think. Honestly the 2.0 is a very capable car, and while I never owned a 2.0, it seems like the 2.1 is only a little better in some areas. The differences between the 2.0 and the 2.1 are the front castor blocks, rear drive shafts (longer) and the rear hubs.