either the picco 26 or hyper 8 port. the There both under $200 and i highly recomend them i have a savage with a hyper 8 port in it and it fly's. I'm in the process of putting in a picco 26.Hope i helped.Oh and when you upgrade the engine you probly will need to upgrade the dogbones to some titianium one's and any plastic drivetrain parts such as gears will need to be replaced with steel or titianium one's being that with a bigger more powerfull engine you will definitly strip some gears . i know i did when i got my hyper 8 port. hope i helped.