This certainly would have been interesting had it happened:
The last Argentine dictatorship headed by General Leopoldo Fortunato Galtieri had plans to attack Chile following the invasion and recovery of the disputed Falklands/Malvinas Islands in 1982 revealed on Sunday the former chief of the Argentine Air Force at the time, Brigadier Basilio Lami Dozo.I'm not sure how credible or believable this is. So far as I know, it's the first time any mention of a possible Chilean-Argentine war has ever appeared. Certainly, it's not out of the question. Just because both countries were led by right-wing murderous dictatorships in the late-1970s and early-1980s did not mean that they were always on the same page, and diplomatic tensions flared up at the time over some border disputes. However, Dozo's narrative seems a bit strange (and his constant referring to himself in the third-person doesn't make it any more lucid). Argentina more than had its hands full with the Malvinas/Falklands War, and while the dictatorship definitely thought its victory would be quick and assured in 1982 (something recent primary documents from Brazil that I'd been reading support), I can't imagine why the military would want to then turn around and engage in a trans-Andean war with its neighbor. Again, it's not out of the question, and Dozo makes some vague references to hawkish elements. More documentary evidence (rather than just the claims of one former brigadier general among many generals) would really be helpful in understanding this relatively-unexplored aspect of relations between Southern Cone dictatorships. Still, even if Dozo is just making this up, the idea of the effects of a war between Pinochet and Argentina's dictatorship do offer some tantalizing counterfactual and hypothetical scenarios, even if at the end of the day they mean nothing.