Three revolutionaries, remnants of radical underground groups of the 1960s, were convicted today of robbing a Brinks armored car of $1.6 million in October, 1981, and murdering two policemen and an armed guard in the subsequent shootout.

In a theatrical two-month trial, the defendants acted as their own attorneys and refused to challenge the evidence or testimony of 86 prosecution witnesses.

Instead, they called themselves political prisoners, declaring that the robbery was a legitimate "expropriation" designed to finance the creation of the Republic of New Africa, a separate nation in Louisiana, Alabama, Mississippi, Georgia and South Carolina.

Although the robbery took place in Nanuet, in Rockland County, the trial was moved to neighboring Goshen, in Orange County, for fear that extensive publicity would preclude a fair trial.

The defendants convicted by an all-white jury today were Kuwesi Balagoon, the former Donald Weems, 36, a member of the Black Liberation Army, and Judith Clark, 33, and David Gilbert, 39, white members of the Weather Underground, a radical group established in the 1960s.

Two other defendants accused in connection with the same incident will go on trial Oct. 12.

They are Samuel Brown, 41, another Black Liberation Army member, and Kathy Boudin, 40, daughter of prominent civil rights lawyer Leonard Boudin.

A sixth defendant is a fugitive.

Three hours after the verdicts were announced, Boudin and Gilbert were married by a prison chaplain in a five-minute jailhouse ceremony.

The jury had deliberated for four hours before returning guilty verdicts on three counts of second-degree murder and three counts of robbery.

Witnesses testified that the defendants seized six moneybags from a Brinks armored car outside the Nanuet National Bank.

One Brinks guard was shot dead and another wounded.

The robbers fled in a van, then switched to another truck and a car. Police stopped the truck at a roadblock and were sprayed with automatic weapons fire, killing two Nyack policemen.

In closing statements Tuesday, Balagoon, an escaped convict and former member of the Black Panthers, said the three defendants are guerrillas who are "at war" with the United States.

"It's clear the guerrillas intended to shoot police, and that's who they shot. They had to shoot the enemy," he said.

Clark, a veteran of the Weather Underground's Days of Rage in Chicago in 1969, lived with her 2-year-old daughter and two other women on the Upper West Side of Manhattan before her arrest.

"At issue is the right to raise up arms against tyranny," she told the court. "We say it was an attempted expropriation, because revolutionary forces must take from the powers that be to build their capabilities to struggle against the system."

However, Judge David Ritter told the jury, "This is not a trial of political views, but on charges of murder, robbery and larceny."

Sentencing was set for Oct. 14.