Muhannak, who went postward at a more than generous 12-1, prevailed by a head in the inaugural $500,000 Breeders’ Cup Marathon today over Santa Anita’s Pro-Ride synthetic main track. Muhannak, bet down from his morning-line price of 20-1, had won 4 of 7 on synthetics in Ireland and Great Britain and was 1 of 2 at the 1 1/2-mile distance. Difficult to fathom why the 4-year-old gelded son of Chester House went off at double-digit odds. The 7-5 post-time favorite, Sixties Icon, had never run 1 1/2 miles and has been a turf specialist for the first 16 races of his career. Trainer Mike Mitchell saddled the place and show horses, Church Service and Big Booster.