I think the peak (motor) torque is 900/1300 (12v/24v). The graphs do not include a torque curve. You would need to calculate that from the power curve.
Gearbox output torque is motor torque / ratio X approx 93%.
eg for 1/3 ratio 12v motor, the output torque is 900 / 0.3333 X 0.93 = 2511 g.cm or 2.5 kg.cm