Hello Kent. Those are the correct strut cartridges for a stock 240Z front strut housing/hardware. Unfortunately they are not designed for Ground Control coil over kits. GC sells specific cartridges to fit in their kits, and whatever cartridges they are labeling as "Koni Yellow" are not the same as our Koni Sport (Yellow) struts, so they are either a different type of Koni strut (not Koni Sports), or they are from another application entirely (BZ3038, for instance, were for 280ZX front). Even though they do not section the strut housing to shorten it for lowering the car (assuming that is what you meant), that doesn't mean the whole kit hardware is designed for "stock" 240Z strut cartridges.
In addition to the height of the cartridge, the cartridge you need is also dependent on the strength of springs you will be using with the coil over kit. Do you know the springs that are on the second hand kit you purchased? I'm not sure if anybody who has ordered the Ground Control kit can tell you what number of Koni strut cartridge they were sent from GC, but they are not 240Z front Koni Sport Yellows as we sell.
If you are not racing this car, and want to use these with your Ground Control front coil over setup, and your measurements indicate that removing part of the "nub" would be enough height, then it is possible, although not recommended, and one would need to be very careful. The warranty would be void for modifications, just like it is for racing applications, so consider carefully if you decide to use these for a custom setup. Here is what a qualified technician said:
Again, if this is a race car, or you have a specific level of "race" type performance in mind, Ground Control has strut options designed to match the "race" strength of the springs, AND fit with their specific hardware/camber plates/etc.
Let us know what you decide and how we can help.