I don't know if the MT car is too short, but it's clearly sitting too high -- notice the white overheight line. Those should line up. The 60' car needs to come down a LOT to have the bottom of its white line match the line of the 86' car.
Should it be taller even after lowering to match the height of the 86' car? I don't know the scale height. But I bet even if it is, MT didn't do that because to get the proper height on top of the higher truck stance, the thing would be WAY over-dimensional and likely not fit through a lot of bridges and tunnels.