President Reagan has moved to fill two top jobs at the Agriculture Department.

On Friday, the White House announced that Reagan would nominate Vance L. Clark, a retired Bank of America official, to head the Farmers Home Administration. Clark, 61, of Fresno, Calif., is a board member of the Producers Cotton Oil Co. and a commissioner of the California Student Aid Commission.

Clark retired from Bank of America in 1983 after a 42-year career. He was the bank's senior regional vice president in the San Joaquin Valley, a major agricultural region in California.

Raymond D. Lett, executive assistant to Agriculture Secretary John R. Block, was named as Reagan's choice to succeed C.W. McMillan as assistant secretary for marketing and inspection. Lett, 49, served with Block in the Illinois Department of Agriculture.

The White House also said Richard S. Nicholson, a career staff member of the National Science Foundation, would be nominated to be an assistant director for mathematical and physical sciences.

In addition, Joyce A. Doyle, assistant general counsel of Belco Petroleum Corp. in New York, will be nominated to the Federal Mine Safety and Health Review Commission.

Arlene A. Triplett, associate director for management at the Office of Management and Budget, has resigned, effective Aug. 1. Triplett reportedly wants to explore opportunities in the private sector.

At the FBI, Oliver B. Revell, a 20-year bureau veteran who was a key supervisor in the Abscam investigations, has been promoted to executive assistant director for investigations. Revell will serve as FBI Director William H. Webster's principal deputy for criminal, investigative, intelligence and counterterrorist activities, the bureau said.

Revell fills a post that has been vacant since 1981, when Francis (Bud) Mullen moved to head the Drug Enforcement Administration.

The bureau also announced that John A. Mintz, a 24-year veteran, has been named executive assistant director of administration. He succeeds Lee Colwell, who will retire Aug. 2.

Floyd I. Clarke, a 21-year veteran, was named assistant director of the FBI's criminal division, succeeding Revell.

At the General Services Administration, A.C. Arterbery has been appointed associate administrator for operations by the agency's new administrator, Terence C. Golden. The decision effectively forces the incumbent in that position, Charles Davis out of the job, despite a promise from Golden last week that he would have up to three months to help Golden screen replacement candidates for the post. Arterbery is now with TRW Inc., a major defense contractor, and was confirmed by the Senate last year for a part-time post as a member of the board of directors of the African Development Foundation.