Imperial Bank plans to acquire control of Countryside Bancshares of Sacramento in exchange for Imperial's thrift unit, Southern Pacific Thrift & Loan of Beverly Hills. Countryside is the parent of Countryside Thrift & Loan, which has assets of $22 million. Southern Pacific, with assets of $4.9 million, would become a wholly owned subsidiary of Countryside Bancshares. Imperial and Countryside signed a letter of intent that would give Inglewood-based Imperial more than 51% of Countryside's stock, worth about $2 million. The transaction requires approval by regulators and Countryside shareholders.