i runnuing a 325 mg servo in my savage for gas and brake does this have enough power to stop the truck or sholud i use a 645 mg

I believe you mean the HS-325HB servo.

This servo only has a torque rate of 42 oz/in. The 645 has a torque rating of 107 oz/in. The 645 would be a much better choice in my opinion but is also slightly overkill for a throttle/ brake.

yes you are correct on the servo number .. i have the truckzilla kit installed on my savage .