Anything from 7t-17t should be fine for drifting, the lower the turns the faster the motor. All up to your budget. Servos, digital or metal gear it doesn't matter too much on a lightweight car. a 5000mah NiMh battery will last the longest but if you go lipo you can get higher MaH.

As far as your chassis, in the future you might want to lock the rear diff, switch out the gears and maybe improve the steering angle.

By the way, my family's from Cork