After the war, larger construction equipment was needed in order to reconstruct and cultivate devastated farmlands. At this point, Japan was developing equipment imitating what the U.S. army had brought in.
Larger graders were in demand under the nation's "5 year maintenance and repair plan of roads and streets".
Also as the number of large scale domestic construction projects grew, large equipment was more in demand for engineering work, such as building roads and water channels, which led to the opportunities for development of graders that were of a larger class than GD30. By the way, the number that came with the product name signified the length of the blade on those models. For example, GD37 meant its blade length was 3.7m.
Around this time, graders began to be used for snow removal more frequently, and they were equipped with a sealed driver's cab, heater, snowplow, side wing, and snow blower.
There were other construction machines built by Komatsu over the years. We can see how the various designs mirrored different eras if we look at them set against the flow of history.