Just got a brushless edition Revo!

[lincpimp]

For parallel wiring connect both pos leads to each other and the same with the neg leads. That will double your mah and keep the voltage the same. Series wiring is the oposite, where you connect the pos of one pack to the neg of another. That doubles the voltage, and the mah stays the same.

I will also suggest 5s for that truck, and the swaybar kit. Sounds like you could go up one color on the springs too, as they sound a bit soft.