Yes, you will need donor kunckles. For what it's worth (not 100%), Rock Auto lists the same left knuckle for the base and SS/SC models. I do believe they use the same wheel hub and struts, and off the top of my head the lower control arms are different between the two models but completely swappable, which does not disagree with the knuckles being interchangeable. You should be able to grab a pair from a junkyard for pretty cheap from any (non-SS/TC) Cobalt.
SS/TC knuckles are definitely different from base model and SS/SC knuckles, keep that in mind.