Fred Fielding, chief assistant to White House counsel John Dean in the Nixon administration, yesterday was named White House counsel to President Reagan.

Fielding, who served in the transition as conflict-of-interest counsel and headed a transition team for the Office of Government Ethics, left the Nixon White House early in 1974, and was not connected with any wrongdoing in the Watergate scandal that doomed that administration. He was, however, a frequent conveyor of messages and money in the Watergate period, and Dean testified in the Senate Watergate hearings that Fielding once acted as an innocent messenger in carrying $350,000 in cash from the Committee for the Reelection of the President to top Nixon aide H.R. Haldeman.

Haldeman later speculated that Fielding was the mysterious "Deep Throat" who helped Washington Post reporters Bob Woodward and Carl Bernstein break the scandal. Fielding emphatically denied it.

Reagan also announced yesterday the nomination of Washington lawyer M. Peter McPherson, a White House aide in the Ford administration, as administrator of the Agency for International Development. McPherson is a former Peace Corps volunteer and tax law specialist for the Internal Revenue Service, and was general counsel to the transition.

Several State Department appointments also were announced: Walter J. Stoessel Jr., U.S. ambassador to West Germany, as undersecretary for political affairs; former New york senator James L. Buckley as undersecretary for coordination of security assistance programs; Washington lawyer Richard Fairbanks, a top transition aide, as assistant secretary for congressional relations: Richard T. Kennedy, a member of the Nuclear Regulatory Commission, as undersecretary for management, and Robert C. McFarlane of the Senate Armed Services Committee staff as counselor.

Other appointments:

Joseph F. Wright Jr., a Citicorp executive, as deputy secretary of commerce.

Ray Barnhart, a Texas insurance agent and state highway commissioner, as head of the Federal Highway Administration.

Raymond A. Peck Jr., vice president of the National Coal Association, as head of the National Highway Traffic Safety Administration.

Edwin W. Thomas, a former California aide to Reagan, as assistant counselor to the president.

Beryl W. Sprinkel, a Chicago bank executive, as undersecretary of treasury for monetary policy.

James C. Miller, a resident scholar of the American Enterprise Institute's Center for the Study of Government Regulation, as associate director of the Office of Management and Budget.

C.W.McMillan, an executive of the National Cattlemen's Association, as assistant secretary of agriculture for marketing and transportation services.

Lee L. Verstandig, an aide to Sen. John H. Chafee (R-R.I.), as assistant secretary of transportation for governmental affairs.