As the question says what if both Peru & Venezuela both threw their lot in with Argentina in '82? . . . especially trying to attack British Forces and landing supplies and reinforcements on the islands.
I could possibly see Venezuela taking advantage of the situation to make a play for western Guyana, or Guatemala sneaking into Belize, but what's in it for Peru?
Ok I don't have the sources but I remember reading that Peru was vital in helping Argentina fough the air war by being the vehicle through which Israel supplied the Argis with drop tanks. As with many things more the Junta had not take care of having a decent supply reserve of them. And the poor courageous Argis pilots were forbidden to drop them (at least in the attack squadrons) without being attacked first.