Well, Argentina was in an almost perpetual state of chaos since the 60s with a serie of right wings coups or left wing guerrillas devasting the economy and ripping apart the society, so another radicalization like 1976 was just waiting in its wings.
It would be hard to avoid a coup in Argentina but maybe with one of the PODs below could have helped the Argentine military dictatorship being less violent than in OTL.
a) No Isabela: Isabela Peron was a political disaster and had no qualification to assume the Argentine Presidency other than being Peron's third wife. Another person as VP could have helped to stabilize things better than Isabela after Peron death in 1974.
b) Peron living until 1976. A hard POD given Peron's precarious health in 1973 - 1974. If Peron managed to live two years more, maybe he could have isolated and weakened the most radical parts of Peronism - the Motoneros while crossing political lines to form a kind of national unity government with the UCR of Ricardo Balbin. If the decline of Peron in 1975-1976 was somewhat slow, he even could have pushed for early elections (like Isabel tried to do in OTL) in order to elect Ricardo Balbin, forcing the Peronists to adopt more centrist policies.
c) Italo Luder President in 1975: Italo Luder acted as President during a Isabel sick leave and during the brief President, he acted much like Uruguay's Juan Maria Bordaberry, giving full powers to the Military to persecute the guerillas. If Italo stayed on power, his government could have become very similar with the Uruguayan Civic -Military Dictatorship, where a "nominal" civil President acted just a rubber stamp to the Military.
With a "weaker" Dictatorship, the Falklands / Malvinas war would be surely avoided as the military government would not have the enormous internal power and control over the Argentine society that it had in OTL in order to embark in an adventure like the Falkands / Malvinas war was.