Received my V1 Shilka in the mail today from SprueBros. On the sprue layout in the instructions, there is only one sizeable part that is greyed out as not used. Appears to be a hatch or other access door. That's it. So there really is not a multitude of parts left over for 1 of 2 versions in one box.
No matter to me, as I simply wanted a 1/35 ZSU-23-4 for the display shelf. I'll happily build the V1 versus the M, and did not have a particular preference anyways. But maybe for someone searching for info on the kits in the future, it will help to know that the boxings do appear to be different versions. For the record, the V1 kit I have comes with the following labeled parts trees (vehicle identifiers are stamped on the sprues themselves):
Tree A: indie track sprue, is marked as 'ZSU-23-4'
Tree B: hull sides & engine grille, is marked 'ZSU-23-4V1'
Tree C: lower turret & radar sprue, is marked as 'ZSU'
Tree D: upper hull & turret sprue, is marked as 'ZSU-23'
Tree E: guns & roadwheels, no other tree markings other than 'E'
lower hull is seperate & unmarked
Apparently, it appears that parts on tree B are specific enough for the V1 version only. Curiously, the tree with the guns on it is not marked for any version -- one wonders if this tree could differ in the M boxing, since the guns were one of the Shilka's upgrades there. The rest of the sprues appear to be marked to be boxed in either kit.
The V1 boxing includes decals for Egypt, Czechoslovakia, East Germany, Poland, USSR, Afghanistan, and Hungary.