John Mantley, writer-exec producer of some of the most successful shows in television history, died of heart failure Jan. 14 at his home in Sherman Oaks, Calif. He was 83.Best known for his work and guidance on legendary “Gunsmoke,” “The Wild, Wild West” and miniseries “How the West Was Won,” Mantley was inducted into the Producers Guild of America Hall of Fame in 1992. All in all, he exec produced more than 500 hours of primetime television. Toronto native was born to biz parents and was the cousin of silent film star Mary Pickford. He got his B.A. from U. of Toronto and went on to receive his M.A. in theater arts from the Pasadena Playhouse, where he graduated magna cum laude. After appearing in two pics, “The Secret Fury” and “Three Came Home,” in the early 1950s, he focused on writing and producing. His started in television dramas in 1955 as a producer and story consultant on “Gunsmoke” (and its half-hour edited version “Marshall Dillon”) and helped to guide it on its record-breaking 20-year run. During the 1950s he also wrote for “Desilu Playhouse,” “Rawhide” and “The Untouchables.” He found success as an author as well. His sci-fi novel “The 27th Day” was adapted into a 1957 feature by Columbia, with Mantley penning the screenplay. Another of his novels, “The Snow Birch,” was turned into the pic “Woman Obsessed” two years later. His screenplay “My Blood Runs Cold” was also made into a 1965 feature, starring Troy Donahue and Joey Heatherton. Indeed, Mantley spent much of his career moving between sci-fi and oaters. He needed a background in both when he became a producer on “The Wild, Wild West” in 1965 and helped rescue the surreal action skein from sagging ratings. The following year he returned to “Gunsmoke” and stayed with the show through 1968. He then produced the ’68 feature “Firecreek,” which starred James Stewart and Henry Fonda. He wrote and produced the ’77 and ’78 minis of “How the West was Won,” then returned to sci-fi as a producer on “Buck Rogers in the 25th Century” and the hybrid actioner “MacGyver.” He was additionally commissioned by ABC to write the 22-hour miniseries bible for James Michener’s “Texas” and the bible for mini “Sam Houston.” His final credits were as producer and exec producer on “Gunsmoke” telepics in ’87 and ’90. Besides the Producers Guild Hall of Fame, he garnered many awards in his long career, including the Golden Spur from the Western Writers Association, and special salutes from AFI and ATAS. He was especially proud of his Certificate of Extraordinary Merit from the President’s Council on Mental Retardation. He is survived by his wife Angela; daughter Maria Marill, VP of studio operations at Sony; son Clay; and a granddaughter. Memorial services will be held Tuesday at the family’s home in Sherman Oaks. For details, call (310) 202-3445.