Clayton McDonald''s second-half header saw non-league Grimsby Town shock local League Two rivals Scunthorpe United in a thrilling FA Cup first-round replay. The visitors went ahead when Lenell John-Lewis turned and shot low to convert Aswad Thomas''s left-wing cross. Ross Hannah went close three times for Grimsby, before Terry Hawkridge''s deflected shot hauled Scunthorpe level. But Scott Kerr''s free-kick was met by McDonald as the Mariners earned a second-round tie with Northampton Town.