John W. Ditzler, director of the Veterans Administration medical center in San Diego, is expected to be named chief medical director of the VA's Department of Medicine and Surgery on Thursday. VA Administrator Harry N. Walters chose Ditzler, 68, who joined the VA in 1972, from five candidates recommended by a VA committee. Ditzler will oversee a division that has a fiscal 1985 budget of $9 billion and nearly 200,000 employes. He replaces Donald L. Custis, who resigned in May.

President Reagan has nominated Richard H. Jones to be deputy administrator of the Federal Aviation Administration. Jones is an active pilot with Eastern Air Lines and a member of the Air Line Pilots Association, a union that has frequently been critical of FAA's safety efforts. He is also a practicing attorney who has been a plaintiff's lawyer in a number of civil suits where the government was a defendant.

At the Health and Human Services Department, Edward N. Brandt, assistant secretary of health, announced that he would resign at the end of the year to become chancellor of the University of Maryland at Baltimore. Brandt, who also headed the Public Health Service, had previously served at the University of Texas.