Sometimes the difference in an Arena Football League game is minuscule. Good thing the Spokane Shock had a safety net to work with from midway through the first quarter. The Shock benefited from an early safety, built a 19-point lead and held on for a 60-57 victory over the Milwaukee Iron to claim the National Conference championship in front of 8,151 Thursday at the Arena. The victory puts the top-ranked Shock (15-3) into the ArenaBowl next Friday at 5 in Spokane. The Shock will host the winner of Saturday’s Tampa Bay-Orlando game.