Security Pacific Corp. of Los Angeles yesterday completed its takeover of American Finance System in a $65 million exchange of stock and cash.

AFS, a consumer finance company based in Silver Spring, is now a subsidiary of the giant West Coast bank holding company.

In its first action as owner, Security Pacific named William F. Ford to be chairman and president of American Finance. Ford also will continue as chairman and president of Security Pacific Finance Co., a subsidiary of the Los Angeles firm.

American finance specializes in small consumer loans at 369 offices in 22 states, and will continue to have its headquarters here. Security Pacific Finance has 93 offices and makes larger loans, an AFS spokesman said.

Under terms of the acquisition, approved last week by the Federal Reserve Board, the $20-billion Security Pacific will advise AFS shareholders later this month of procedures to exchange and redeem their shares.

Each of the 4.9 million shares of AFS common has been converted to 3215 share of Security Pacific and each of 369,000 shares of 6 percent cumulative preferred has been converted into $30.50 of cash. For each of the 40,000 shares of $6.75 cumulative preferred, owners will receive $127.37 in cash.

Security Pacific, the nation's 11th largest banking company, has assumed all obligations of the Silver Spring company.