COLOR PHOTO: DALE BLACKWELL Gordon Hartshorn GRAND PRAIRIE, TEXAS Hartshorn, 58, ran a marathon a week for 74 consecutive weeks. He raced in 24 states and six Canadian provinces or territories during the streak, which began in February 1996 in Louisiana and ended in July on Baffin Island, 450 miles north of the Arctic Circle. He has completed 224 marathons.