A longstanding policy dispute within El Salvador's largest guerrilla faction has eased substantially with the consolidation of a position emphasizing unity with other factions and openness toward cooperation with outside groups, according to senior officials in the rebel movement here.

The new orientation is reflected in the choice this week of two new top leaders of the faction, called the Popular Liberation Forces, who generally have favored flexible positions, the sources said. They added that a third leader, identified with a more dogmatic position, was demoted.

The Popular Liberation Forces is one of five insurgent groups making up the Farabundo Marti National Liberation Front that is fighting to overthrow the U.S.-backed government of El Salvador.

The new first and second secretaries of the faction's central committee--Leonel Gonzalez and Dimas Rodriguez, respectively--replace two long-time leaders who died here in April in a bizarre set of events that reportedly included a ritualistic murder and a suicide. The violence marked the culmination of the differences between the two currents of opinion in the faction.

The new leaders were elected about a week ago in guerrilla-controlled territory in Chalatenango province, the sources said. At the same time, the faction endorsed a policy statement favoring cooperation with other factions and the "wide participation" of other Salvadoran social and political groups in the insurgent movement, they said.

It is virtually impossible for a U.S. correspondent to confirm accounts of policy debates within the Popular Liberation Forces, known by its Spanish initials FPL. Rebel sources who speak to North American reporters have an interest in portraying the guerrillas as unified and willing to negotiate.

If the accounts obtained here are correct, however, the Popular Liberation Forces has put behind it a tendency toward ideological dogma and aloofness from other groups. The shift, which has been developing for at least two years, has tended to reduce frictions with the rebel movement's other four military factions and with Nicaragua's ruling Sandinista National Liberation Front, the sources said.

The sources noted that a more unified guerrilla movement is in a better position to negotiate with the Salvadoran government and with the United States. As the Popular Liberation Forces has been shifting its stance this year, the Farabundo Marti Front has begun talks with both governments.

In one sign that the movement is pulling together, the other major Salvadoran guerrilla faction, the People's Revolutionary Army, issued a statement broadcast over the guerrilla radio station Radio Venceremos welcoming the Popular Liberation Force's selection of a new leadership.

The principal division within the Popular Liberation Forces was between the two leaders who died in April--the faction's founder and leader, Salvador Cayetano Carpio, and second-ranking official, Melida Anaya Montes.

Cayetano Carpio, known as "Marcial," uncompromisingly favored a strategy of "prolonged popular war" modeled on the strategy of the Vietnamese Communists. He resisted any modifications to his theories to the extent that cooperation with other guerrilla factions in the field was difficult. In one celebrated case in March 1982, the Popular Liberation Forces did not join other factions in launching a major offensive.

Cayetano Carpio viewed leftist political groups only as potential allies in a tactical sense rather than as long-term partners. One source said he also was skeptical of some diplomatic initiatives favored by Nicaragua, a principal backer of the Salvadoran rebels.

"Marcial was father and grandfather to all of us in the FPL, but he didn't really see the best way to carry out the war. His positions were rigid and intransigent," a well-placed guerrilla leader said. Anaya Montes, known as "Ana Maria," gradually evolved as the leader of a group within the Popular Liberation Forces favoring greater flexibility. Her positions were described as "more interested in unity" and "generally more positive."

The selection of the new leadership and adoption of the new policy statement mean that "the line of Ana Maria has been consolidated," according to a senior movement leader with a moderate outlook.

The new leaders, Gonzalez and Rodriguez, were identified as supporters of Anaya Montes' positions. After the deaths in April, Gonzalez and Rodriguez had been named provisionally to the top two positions.

At the same time, a third leader, Salvador Guerra, was named provisionally to a post that is the rough equivalent of minister of defense. A senior source said that he was considered to be more supportive of Cayetano Carpio's positions than the others.

In some recent Popular Liberation Forces documents, Guerra's name was said to have appeared above those of Gonzalez and Rodriguez. At the recent meeting of the revolutionary council in Chalatenango, however, Guerra was removed from his defense position, which was given to Rodriguez instead.

A high-ranking rebel leader said that the policy statement, departing from Carpio's line, urged alliances with nonguerrilla organizations like labor unions and professional organizations.

Gonzalez, the new leader, has a background as an educator and political organizer. Rodriguez, a university student before he joined the faction, has led guerrillas in the field.

The selection of the two ended a period of uncertainty about the faction's leadership that began with April's events. At that time Anaya Montes was stabbed to death by a group allegedly led by Rogelio Bazzaglia, a guerrilla commander who was close to Cayetano Carpio. Other leaders concluded that Cayetano Carpio's policies were responsible for the murder, if indeed he had not ordered it. After it reportedly was made clear to him that his career was over, he shot himself.