Details of an alleged conspiracy to murder slain investigative reporter Don Bolles and two others - including Arizona's attorney general - were revealed today following th arrest of two persons who were charged with first-degree murder in the case.

About the same time, John Harvey Adamson, 33, a Phoenix greyhound racing dog owner, in a change of plea, confessed to a Pima County judge in Tucson that he placed a bomb beneath Bolles' car June 2, 1976, minutes before it was detonated by remote control as the reporter attempted to back from a hotel parking space.

Bolles died 11 days later. He had gont to the hotel to meet Adamson on the promise of a news tip.

Charged today with first-degree murder and conspiracy to murder in connection with Bolles' death were Phoenix contractor Max Anderson Dunlap, 47, and Chandler, Ariz., plumber James Albert Robison, 54.

Phoenix homicide detective Jon Sellers, key investigator in the case, said today there is "nothing to indicate the Mafia or Emprise (a New York-based sports concession operation) were involved in the crime."

Bolles muttered both of those names and that of Adamson as rescuers rushed to his aid.

Adamson's admission of guilt was part of a plea agreement entered into by the state of Arizona and Adamson. While he originally was arrested on an open charge of murder, his guilty plea today was to second-degree murder.

In return Adamson was promised that his prison term would be served in an institution outside of Arizona and would be a minimum of 48 years and a maximum of 49 years.

State Attorney General Bruce Babbitt said "The term of 48 to 49 years was arrived at to assure that Adamson will serve a certain term of 20 years and eight months in prison with no chance for release prior to that time."

The purpose of getting Adamson out of Arizona apparently was to ensure his personal safety.

In entering his plea today, Adamson told County Superior Court Judge Ben. C. Birdsall in Tucson that "I placed a bomb containing dynamite underneath the vehicle driven by Donald F. Bolles to be denonated at a later time for the express purpose of killing him. He died 11 days later. I telephoned an individual where Bolles would beat a specific time and made arrangements where the bomb would be detonated."

His new plea immediately ended his murder trial in Tucson which had started two weeks ago, and for which jury selection had almost been completed.

Sellers said, "There is no bout in my mind the person who detonated the bomb was Robison." He said the plumber "probably was in a vehicle at the southeast corner of the parking lot" where the blast occurred.

In affidavits and in interviews, the detective said he believes events leading to the murder occurred as follows:

Dunlap allegedly asked Adamson in March, 1976, to kill Attorney General Babbitt and another man" . . . at the request of Kemper Mrley."

Marley, a 70-year-old millionaire Arizona land-owner and wholesale liquor dealer, had been the target of several Bolles investigations over the years. The latest was last spring, when Bolles reported on Marley's controversial appointment to and subsequent resignation from the Arizona Racing Commission.

Maryley's appointment became an issue after Bolles pointed out prior irregularities surrounding Marley's activities at times he served in other state positions.

Dunlap, in a subsequent conversation with Adamson, allegedly noted that Marley . . . "wanted Don Bolles killed as a result of . . . Bolles having given . . . Marley a bad time over the Arizona Racing Commission . . ."

At that time, Adamson allegedly replied that it would cost $50,000 plus expenses - paid in cash - to kill all three persons. The third man allegedly singled out for death was Alex Lizanetz, who is believed to have formerly worked for Marley and who testified against him in the commission hearings. Lizanetz is known as "King Alphonzo," and is so identified in Sellers' affidavit.

Sellers said investigations have some idea as to why Bolles was picked as the first victim, but said he could not discuss it.

Dunlpa allegedly paid expenses to Adamson in two payments totaling $3,000 and made an additional $5,800 cash payment eight days after the bombing, but before Adamson had been charged with murder.

Dunlap told police in July he delivered between $5,000 and $6,000 to Adamson after a man he did no know brought the money to his home early on June 10.

Robinson allegedly constructed the bomb which Adamson placed under the car shortly after discussing final plans with Dunlap outside the office of a Phoenix attorney.

Asked it Marley will be charged in the case, Sellers said "the investigation is continuing into the allegations regarding Kemper Marley".

Marley could not be reached for comment today, and his wife said he had gone to his farm.

Sellers said Dunlap and Robinson refused to answer questions when arrested today. They were being held without bond, and a preliminary hearing on their charges was scheduled for Jan. 24.

As part of the plea agreement, Babbitt said, Adamson has promised to give his "full and truthful cooperation" to authorities in prosecuting the Bolles case and certain other cases. Sentencing will be deferred, said Babbitt, until "after Adamson has fulfilled his agreements to testify as a witness for the state."