Dr. Gerard Noel Burrow, chief of medicine at the University of Toronto and chief physician at Toronto General Hospital, has accepted a position as dean of the medical school at the University of California at San Diego. The 54-year-old endocrinologist said he plans to begin about March 1 if his appointment is confirmed by the UC regents; they are expected to consider the matter in November. Burrow would succeed Dr. Robert G. Petersdorf, who resigned last September to head the Assn. of American Medical Colleges in Washington. Before going to Canada, Burrow, a Boston native, was a professor of medicine at Yale University for 10 years.