VACAVILLE, Dec. 21 — A California Medical Facility administrator has recommended that convicted mass murderer Charles Manson remain in the Vacaville prison.

“But I want to keep the option of sending him back to San Quentin if he becomes a management problem,” said Edward George, program administrator of CMF’s Willis Unit, where Manson is undergoing psychiatric study.

Manson was moved to Willis Unit May 11 for evaluation after he “became extremely withdrawn” in Folsom prison, according to a CMF spokesman.

He was switched to a tighter-security psychotic ward in the Vacaville prison Oct. 9 after yelling death threats at guards, refusing to eat for fear his food was poisoned and exhibiting other “bizarre and unusual behavior,” the spokesman said.

Manson now is back in Willis Unit, where he is allowed to mingle with some other prisoners, and is “doing very,” George reported.

“My personal opinion is that we’ll end up retaining him in Willis Unit as a Category L case, a Iong-term psychotic in remission who’s not willing to be in therapy.

“We feel he is lucid, but he can flip out, either on purpose or otherwise. He changes a lot. He’s moody and can carry a game on for a long time,” George stated.

George said he will write his report on Manson to the California Department of Corrections Review Board this week. The board will decide where to place him.

Manson, according to George, “seems indifferent” about where prison authorities send him.

“He says he wouldn’t mind going back to Folson, but he says he’s okay here, too.”

Manson now spends most of his time in his cell, writing letters, and reading letters, newspapers, magazines, books on ecology, and the Bible, George reported. He is allowed to correspond freely with most adults, but not other prisoners such as Manson followers Sandra Good and Lynette Fromme, and all his mail is censored, the administrator said.

Manson’s correspondence with Miss Good and Miss Fromme was cut off after Manson wrote to a Vacaville newsman in August claiming to have “sent a list of people out to be murdered,” he said.

George said he last week gave orders that Manson be allowed to play a guitar in his cell several hours a day, one of Manson’s longest-standing wishes.

“He’s happiest when he’s left alone,” George said.

Manson, now 42, was sentenced to the gas chamber, along with three women Manson Family members, after they were convicted of the bloody murders of actress Sharon Tate and six other persons in Los Angeles in 1969.

Their sentences were reduced to life in prison after the California Superior Court ruled the death penalty unconstitutional.

By state law, Manson will be entitled to a parole hearing in 1978, but prison system officials say there is no chance he will be released.