My grandfather had a stroke. His carotid arteries are 100% and 85% blocked. What kind of surgery does he need?

Depends. We do not perform surgeries to open up complete (100%) blockages. For the side with 85% blockage he should first and foremost be on an Aspirin as well as a cholesterol lowering statin medication for optimal medical management. The surgical options are an open carotid endarterectomy or a carotid stent. If he can tolerate anesthesia then an open procedure is preferred.
Stent. With one side blocked he should be evaluated to have a carotid stent with distal protection on the 85% side.