Redefine AXIS2 to change the range of values and suppress all axis elements. Setting all the label and tick mark options to NONE and assigning a line style of 0 removes the response axis. NOPLANE removes the 3D axis plane. Specifying ORDER= makes all the graphs use the same range of values. 
axis2 order=(0 to 250 by 50)
      label=none
      value=none
      style=0
      major=none
      minor=none
      noplane;