The differances are......Longer steering linkages, updated tranny cases (internals are the same), longer front driveshaft, P2 rockers, engine brace, 3.3 engine, wide ratio 2nd gear,and newer rims. Impact RC has a kit for $99.99 that comes with all the major parts to turn a 2.5 into a 3.3. Trans cases, dront driveshaft, engine brace, steering arms, body and chassis. Not a bad deal

You dont need the trans case but it has the positions to install the rear brake onto it. I you dont run a center diff then you dont need it.