January 12, 1983

Treasury Secretary Donald T. Regan is preparing two sweeping tax reform proposals for possible inclusion in President Reagan's State of the Union address, although legislation to put them into effect might be delayed until 1984, Administration officials said today. Both proposals would broaden the tax base and close loopholes, which many Republicans and Democrats have advocated, and would make it possible to increase tax revenue while lowering tax rates, the officials said. One of the proposals under consideration would replace the graduated income tax with a flat-rate tax system. Such a system would tax income at a single fixed rate, or several fixed rates, without most of the deductions that are now available to reduce taxable income, the officials said.

Dr. Barney B. Clark's condition has improved to the point where he might leave the hospital as early as three weeks from now, but with ''significant lung and kidney impairment,'' his doctors said today. Dr. Clark is ''significantly more lucid, communicating more and physically stronger,'' Dr. Chase N. Peterson, vice president for health sciences at the University of Utah Medical Center, said at a news conference. Dr. Clark became the world's first recipient of a permanent artificial heart 41 days ago. The Jarvik-7 artificial heart has been working well and there is no evidence of infection, the doctors said. At the news conference, the first in two weeks, Dr. Peterson and Dr. Lyle Joyce, one of Dr. Clark's doctors, left an impression of cautious optimism, with more emphasis on the optimism.

The nation's leading banks, in an action that lagged considerably behind a sharp drop in the cost of their own funds, lowered their prime lending rates yesterday by half a percentage point, to 11 percent. The banks attributed the delay to uncertainty about the cost of new money market accounts for consumers and the possibility of large losses from loan defaults. The prime rate cut was widely expected because of the unusually big gap between the interest rates banks have been paying for their own funds, about 8 1/2 percent, and the interest rates they have been charging on loans to their medium-size and small corporate customers, which range upward from 11 1/2 percent. In response to the falling cost of money, the Chase Manhattan Bank lowered its prime rate to 11 percent as early as Dec. 28, but no other major bank followed until yesterday.

The first known theft of secret data on the nation's money supply from the Federal Reserve Board's computers was discovered because an alert employee questioned the apparent use of the computer by a fellow employee who was then on vacation. Details of the theft and subsequent attempts were disclosed today in Federal District Court here when Theode C. Langevin, a former Fed employee, pleaded guilty to tapping illegally into the central bank's computer on his first day as a ''Fed watcher'' at the E.F. Hutton brokerage firm in New York. Discovery of the first theft, on the night of Nov. 22, 1982, was fortunate, said an Assistant United States Attorney, William S. Block. He said that on the morning of Nov. 23, Carol Keyte, an employee in the same division where Mr. Langevin had worked, noticed that the last recorded use of the computer was by Wayne Smith, who was registered by his name and used the secret password ''PAZ.''

Secretary of Defense Caspar W. Weinberger announced today that he had recommended to President Reagan an $8 billion reduction in military spending proposed for 1984 to help cut the projected Federal deficit of about $200 billion. ''In response to economic problems,'' Mr. Weinberger told reporters at the Pentagon, ''we have agreed before, as we agree now, to modifications in our original program to rearm America.'' President Reagan, speaking in Dallas, asserted that ''we are not reversing our course'' on increasing military power. The President contended, ''It is not setting back in any substantive way at all our defense program, because that still remains our top priority.'' Tepid Reaction in Congress Initial Congressional reaction was tepid, with supporters of increased military spending expressing disappointment and advocates of smaller military budgets asserting that the cut was not enough.