The stock bellcrank is pretty good- its the actual servo & white plastic saver that are poo-poo. I would go onto towerhobbies and order the 'Kimborough servo saver for large gas truck' and the a hitec hs645mg servo- that is what I and alot of other guys use and its a perfect combo. There are other servos available but that one is a great buy-
http://www2.towerhobbies.com/cgi-bin...&I=LXUZ89&P=ML
and the servo saver-
http://www2.towerhobbies.com/cgi-bin...&I=LXS443&P=ML
both those will set you back about $41 + p&p- not bad at all really.