is noticeably smaller.
And those kits are not quite correct to scale, using some of the 1:35 scale models is not a good idea as a number of Tamiya's 1:35 efforts are wrong.
The JS-1 was narrower than than KV, the tracks were also slightly narrower but from what I've been able to work out the the lower chassis was very close to the KV in terms of length. The JS-1 was longer but I think this was down to the shape of the rear, it is steeper and because of this goes out further than the KV rears (early or late).
The JS was also had less ground clearance than the KV but was overall slightly taller.
I am surprised Tamiya hasn't shut down the Hong Kong based companies selling them cheaper than the national retailers yet. It is quite easy to do as well.