Putting K as chassis-code what used previously because it is the platform name, but I am not sure that it is so useful (cf previous discussion about platform names vs chassis codes).
If, as Taxiguy said, the "K" was used in the name and not just as platform name / nick name (i.e. "k-cars"), then we should of course include it in the name. But was it the case for all Reliant/Aries, or only for some years?