Go to HPI web site and down load the MT2 18SS manual and then compare the part numbers with your RTR manual and you will see what you need. This is some and many not be all you need
Savage CB with bearings
4 heavy duty diff cups
2 Heavy duty diff gear kits
Drive cups for spur gear shafts
Front CVD shaft kit
Rear CVD shaft kit on these make sure you get the MT2 SS ones!!!!!!!!!!

Like is said be read to spend around $150 to $200 not including the engine.