While the Type 71 was in the design stage, the Japanese military received partial intel from the U.S.A. about the new Soviet T-64. As a result, they decided to build a more powerful vehicle, designated as the STK-2, alongside the development of the Type 71. The hull and turret were reworked, with the hull front especially reinforced, to increase the level of armoring. In addition, a more powerful engine improved the tank's mobility and crossing capacity. However, the vehicle turned out too expensive and never entered mass production.