I believe the 1940 version that 7dot72mm was referring to was what most people refer to as either the T-26S or T-26E.
Basically, the Russians took a T-26 M39 tank, and applied some extra armor plates (usually bolted, but sometimes welded) to the front and sides of the superstructure, and around the turret, to beef up protection.
This was done mainly for the Finnish front. Only about 80 conversions were done. And no, the kit does not include separate superstructure and turrets with this additional armor plating.
So the kit will support
2,038 M31 (two versions)
2,862 M33 (two versions)
1,363 M38 (two versions)
2,031 M39
552 KhT-26 Flamer
401 KhT-130 Flamer
271 KhT-133 Flamer
That means a single kit will allow the builder to create any one of 10 different versions of 9,518 vehicles. Which I think is amazing. I suspect that other companies would produce a separate kit for each version. So I am very happy with what Rubicon have done here.
This does however mean that you cannot build:
1,823 M36 (two versions)
80 M39S
So out of 11,421 T-26s produced, the kit will let you build 10 of 13 versions, accounting for 83% of the total builds. I have checked over the photos of the plastic sprues, and believe with a modest amount of effort (an hour maybe), the "missing" M36 turret top can be created from the supplied M38/M39 turret top.
If I am right, this will expand the kit to include both versions of the M36, and raise the kit builds to 12 of 13 versions, and 99% of the total builds.
I am quite pleased that Rubicon decided to try and include as many versions of the tank as possible.