A strapping, strikingly handsome leading man of TV series and telefilms and a number of low-budget action features, Mitchell, whose slightly tawny complexion is complimented by his boyish, open features, attracted some attention as a model for the famed and sensuous camera of photographer Bruce Weber while he was studying at New York's National Improvisational Theater. He began landing roles in TV-movies and features during the run of his contract with Weber and enjoyed a breakthrough when he likably essayed the title role in Paul Morrissey's modest study of an ambitious boxer, "Spike of