If you add in K-1515a FAS-DPD chlorine test to a K-2005, it becomes a K-2006. That's the only difference.
As Newdude said, add in the K-1766 and you've got salt testing as well.
Please check the dates on the reagents in that old test kit, and be sure that it wasn't stored improperly (e.g. outdoors in a shed).