City Council members have elected Godfrey Pernell mayor, a post he has held two times before. He succeeds Thomas Heinsheimer. Appointed to the council in 1975 and elected to three subsequent terms, Pernell served as mayor in 1978 and in 1982. Gordana Swanson, another council veteran who has served for 10 years, was chosen mayor pro tem. Pernell, 64, is a dentist and founder-owner of Dental Health Services, a prepaid dental health plan headquartered in Long Beach.