Hey hon, Hep C must be pretty rare in dogs....I don't think I have seen one case of it. I'd recommend calling your vet, though, and asking him/her. I know my clinic does not mind our clients calling to ask things like this, and they can also advise you on treatment for it. I am assuming it would require a treatment/course of meds. Sounds like he is in a rescue group so maybe he is already being treated? If so, call the vet who is treating him. Call the rescue and ask them who is treating him.
I think it's great though, that you want to help!!!!

I wish I could help you more.....