Not being familiar with your needs, we can't give you a proper answer, but the most powerful servo Futaba makes is the S5301, and it has about 21 Kg-cm of torque when run on a 5-cell NiCd or NiMH battery pack.

Full specs are at:

http://www.futaba-rc.com/servos/futm0029.html

When a battery pack is connected to the receiver, the current is sent unregulated to the servos.