SACRAMENTO, Calif., Dec. 23 — One of the last of Charles Manson’s original band has been indicted with another woman on charges of conspiring to mail 171 threatening letters to business and government leaders.

The indictment was issued Monday against Sandra Good, 31, former roommate of Lynette “Squeaky” Fromme, convicted of trying to assassinate President Ford and sentenced to life imprisonment. Susan “Heather” Murphy, 28, a former nurse, was indicted on the same charge, and Miss Fromme was named as an unindicted co-conspirator.

FBI agents arrested Miss Good and Miss Murphy at Miss Good’s apartment soon after a federal grand jury returned the sealed indictment. Their arraignment was scheduled later today but there was some expectation it might be delayed.

As she was driven from her apartment, Miss Good rolled down a window in the back seat of the FBI car and asked, “What about Nixon and his friends and their conspiracy?”

Miss Fromme was Miss Good’s roommate until she was arrested Sept. 5 in Sacramento after pointing a .45 caliber pistol at Ford. Both women were early followers of Manson, the convicted murderer of actress Sharon Tate and six other persons. Most of Manson’s early followers are either in jail or have dropped their allegiance to him.

Miss Fromme and Miss Good have urged a halt to pollution of the earth and say an “International People’s Court of Retribution” would act against polluters. Miss Good said the court had members in major cities around the world.

Last Sept. 11, Miss Good released a list of 70 government and business leaders and firms, saying they were marked for death by such a court unless they stopped polluting the earth.

The indictment accuses Miss Good and Miss Murphy, said to be a more recent convert to Manson’s philosophy, of conspiring with Miss Fromme over at least a three-month period to mail the letters.

It says that on the same day Miss Fromme was arrested, Miss Good and Miss Murphy gave the letters to a friend, Michael Davies, and asked him to mail them. Instead, said Asst. U.S. Atty. Bruce Babcock, Davies turned the letters over to the FBI.

Babcock would not reveal to whom the letters were addressed except to say that they were business and government officials. But he said threats were similar to those made by Miss Good when she released the so-called death list.

The charges carry a maximum penalty of five years in prison and a $10,000 fine. They were held in lieu of $50,000 bond each.

Babcock said Miss Fromme was not indicted in connection with the alleged letter plot because she had already been convicted of trying to kill Ford.

By STEVE LAWRENCE