At 6'5", with broad shoulders and blond hair, Bo Svenson is the American image of the big, lumbering Swede, a part he played in his first American series, "Here Come the Brides" (ABC, 1968-70). Svenson left his native Sweden at age 17 and moved to Wisconsin where he worked on a cousin's farm before joining the US Marines (1959-65). After his military service, Svenson settled in Florida, where he earned his living in various jobs, including professional race car driver. A role in the chorus of a production of "South Pacific" and a guest stint on an episode of "Flipper" convinced Svenson to