LIMA, July 30 (Reuters) - Peru"s Pedro Castillo appointed moderate economist Pedro Francke to the key finance minister post, an olive branch to rattled markets after the newly-elected president earlier named members of his Marxist Free Peru party to several other cabinet positions. Reporting by Marco Aquino, writing by Dave Sherwood; Editing by Raju Gopalakrishnan Our Standards: The Thomson Reuters Trust Principles.