Spelling Entertainment Group Inc. and Republic Pictures Corp. have entered into a definitive merger agreement, which has been approved by the directors of both companies.As previously announced, Spelling will pay $ 13 in cash for each share of Republic outstanding (Daily Variety, Sept. 13). Options and warrants to acquire Republic shares will be converted into rights to receive 1.65 Spelling shares for each Republic share, the companies said. Blockbuster Entertainment, which owns a 63.5% controlling interest in Spelling and 35% of Republic, bankrolled their marriage. The closing of the merger is subject to approval by Republic’s shareholders and other customary conditions. The companies anticipate that the merger will close in early 1994.