Government attorneys agreed yesterday to drop charges against the last two members of the Boston Five still facing trial-William Sloane Coffin, chaplain of Yale University, and author Mitchell Goodman.

The five-Coffin, Goodman, Dr. Benjamin Spock. Marcus Raskin, director of the Institute of Political Studies in Washington; and Michael K. Ferber, a former graduate student here-were charged with conspiring to counsel young men to evade the draft.

U.S. attorney Herbert Travers told the federal District Court in Boston that available evidence-and the acquittal of Spock, Ferber, and Raskin-"does not warrant the retrial of Coffin and Goodman."

Coffin, Ferber, Goodman, and Spock were convicted in June, 1968. Raskin was acquitted. However, a Federal appeals court later set aside the convictions, directing that Ferber and Spock be acquitted and that Coffin and Goodman be given now trials.