Costello, a defender, had his best year in 1956 when he was selected in the All-Australian team at the 1956 Perth Carnival and jointly won West Adelaide's Best and Fairest award with Aldo Rossetto.
Western Australia 11.12 (78) defeated South Australia 7.18 (60), at South Melbourne Cricket Ground , 2 July 1958, crowd: 4,500 Victoria (VFL) 25.17 (167) defeated South Australia 7.7 (49), at Melbourne Cricket Ground , 5 July 1958, crowd: 33,063 Tasmania 11.18 (84) defeated South Australia 11.16 (82), at Melbourne Cricket Ground , 7 July 1958, crowd: 2,760 South Australia 16.15 (111) defeated Victoria (VFA) 5.13 (43), at South Melbourne Cricket Ground , 11 July 1958, crowd: 1,750