Just use the stock gears with the steel idlers Mike sells and you should be good.
http://www.rc-monster.com/proddetail...rod=RCM03idler
The other possible weak spot in the tranny is the cross pin that holds the top gear to the input shaft. It should hold, but if it breaks it usually just snaps clean and you can replace it with a hardened pin or you could jut replace it before you assemble the tranny again and you should be good to go for a long time.