There are 2 different tanks known as IS-4. One of these was an IS-2 rearmed with a long 100mm D-10T cannon. The other IS-4 was a new vehicle projected by LKZ in parallel with the IS-3 by the same design and development bureau. For this second IS-4 the IS-2 hull was lengthened, with an extra set of road wheels added and an improved engine. Both hull and turret armour were increased.
Several alternative armaments were explored in paper studies but ultimately the IS-2's original 122mm gun was retained. An effort was also made to make use of technical data derived from study of the German wartime Panzer V Panther tank, which influenced the layout of the second IS-4's engine cooling system.
The tank was approved for mass production from 1947 to 1949 but due to disappointing speed and mobility only 250 were built. Most of these were transferred to the Russian Far East. In 1949, production was cancelled and later these tanks were removed from service. [Source: wikipedia]
You can download this paper model template here: World of Tanks - IS-4M Heavy Tank Paper Model Free Download