Carotid Artery Block
You should obtain at least a couple of opinions related to this great question.
A blockage alone is not necessarily a reason for surgery. Several major issues to ponder: what other morbidities does your father have (would this or any surgery be safe?), has he had any symptoms related to the blockage (strokes, tias?), and what is the expertise (the complication rates) of the surgeon(s) in your area.