Complex sentence: The vehicle was monstrous, carrying 11 crew in its 100-120ton body, but only one 120ton O-I model was rumored to have been built in 1944 and afterward sent to Manchuria.
Split into simpler sentences: The vehicle was monstrous, carrying 11 crew in its 100-120 ton body. Only one 120 ton O-I model was rumored to have been built in 1944 and afterward sent to Manchuria.