the stock servo is pretty tourkey already. the "must do" is replace the internal tranny gears with steal. the stock xl-5 tranny is all plastic and only last a few months on the 12 turn. steal ideler first, its about $10. steal ringed diff would be next (never blew the diff on mine but after 2 idelers it looked pretty wore). then I would go for sure on the RPM rear hubs with the 5x11 bearings. the stock small bearing dont last very long. as for everything else, just replace as needed. RPM make almost every upgrade part for the rusty and wont bend like aluminum.