The possibility that the Salvadorean Air Force may be strengthened by infusions of more United States firepower is causing a stir here. The dispute divides Salvadoreans into two opposing factions:
* Those who oppose any boost in firepower, which they fear would increase an already-rising level of civilian casualties caused by Air Force bombing.
* Those who rebut this and say that the new gunships will increase accuracy of Air Force actions and hence decrease civilian casualties.
At the center of the dispute are reports from Washington, repeated by American officials here, that the US may be about to equip the Salvadorean Air Force with two modified versions of Vietnam-era gunships.
The tentative plan is to convert two of Salvador's five C-47 aircraft with three 50-caliber machine guns, night illuminators, image intensifiers, and flare launchers. This would turn them into less potent versions of AC-47 gunships, which were nicknamed ''Puff the Magic Dragon'' in Vietnam because of the roar and smoke from their guns.
US officials say the intention is to use the twin-prop planes for night missions and to strike rebel forces which have pinned down government troops in ambush.
The possible acquisition of the modified AC-47s appears to be a rebuff to Pentagon strategists. These strategists, including Maj. Gen. John Singlaub (ret.), have opposed increasing the Salvadorean military's reliance on US technology. Earlier this year Nestor Sanchez, deputy assistant secretary of defense for inter-American affairs, said he was reluctant to send massive-firepower aircraft to El Salvador ''because of our concern over atrocities.'' However, US Gen. Paul Gorman, the chief of the US southern command , has pushed for the use of more powerful gunships against rebel positions in El Salvador, say sources here.
The Salvadorean military hopes to have the aircraft ready in time for a rebel offensive some officers expect will begin soon.
The Air Force is already slated to receive 10 new Hughes 500 helicopters at a cost of some $25 million, raising the number of helicopters in the Air Force's arsenal to 32. Air Force officials also are asking for five new A-37 jet fighter-bombers to bring the number of A-37s to 11.
US officials here contend that the machine guns on the modified AC-47s could more precisely hit their rebel targets than the 250-, 500-, and 750-pound ''iron'' fragmentation bombs now dropped three or four times a day over rebel territory.
''Those who advocate the AC-47 have made the case that they are more accurate than bombing,'' said Thomas Pickering, US ambassador to El Salvador, in an interview, ''in that they can be used to relieve isolated towns and villages under guerrilla pressure because they can get there quickly and they have a long time on station ... and they can work at night.
''So I think all of these things seem to be the major advantages advanced for the AC-47: accuracy, rapidity to arrive, staying power, and the ability to relieve troops under pressure (and) towns and villages under pressure from the guerrillas anywhere in the country.''
Roman Catholic Church officials charge that indiscriminate bombing in recent weeks by the Air Force has resulted in an increase in civilian deaths.
The Roman Catholic archbishop of San Salvador, Arturo Rivera y Damas, has asked the government not to accept the planes: ''It is not my responsibility to dictate war tactics, of which I know nothing. But it pains me as a pastor that innocent people continue to die. This type of warfare seems to be on the increase.''
A classified report published last May by the US Department of Defense Advisory Panel, headed by General Singlaub, is reportedly critical of the bombing practices of El Salvador's Air Force. It also questions the effectiveness of fighter aircraft and heavy ''iron'' bombs to fight an insurgent rebel army, sources here say.
''Dropping 500-pound bombs on insurgents is not the way to go,'' Singlaub told the Associated Press last May. ''There is a need for very discriminate firepower.'' He also said that in El Salvador, ''There is a tendency to escalate to a higher level of violence than is appropriate.''
The modified AC-47 could circle a target at slow speed in a wide arc without interrupting its fire.
El Salvador has five C-47s, the unarmed version of the same aircraft, military officials here say. US Undersecretary of Defense William Schneider Jr. said recently they could be refitted into AC-47 gunships for about $2 million apiece.