Anderson Clayton & Co. said it completed the previously reported sale of American Founders Life Insurance to American Continental for $58 million . . . Chrysler said it has raised the price of imported passenger cars made for Chrysler by Mitsubishi Motors by an average of 1.8% . . . Monumental Corp. reported that it has completed the sale of its wholly owned subsidiary, United Republic Life Insurance, to Life Insurance Co. of Pennsylvania for $30 million . . . Digital Equipment Corp. introduced a new mainframe computer called the VAX 8800 that can process more than 13 million instructions per second. The VAX 8800 operates 12 times faster than the earlier VAX 11780 . . . Dow Chemical and Mitsubishi Chemical Industries agreed to form a joint venture to make and market urethane chemicals in Japan, the companies said . . . Fleetwood Enterprises of Riverside reported that sales for its fiscal third quarter ended Jan. 26 were about $263 million, a decline of 8% from last year's third quarter.