Blown fuse link?
 

I just bought a '77 K5. The battery and starter are both good but I can't start it. The former owner told me he had tried to jump start another car and may have crossed the jumper cables. He saw smoke on the right side under the exhaust manifold and it hasn't started since. Does anyone know if there is a fuselink between the battery and the fusebox that may have blown? Any other ideas would be appreciated.

Have you bench tested the starter? Have you inspected the battery cables? I do not believe that fusible links were used back then.

Yeah, I'm thinking starter myself.