Upvote:2
German wikipedia mentions nothing of an Argentine project predating Leopard 1 development. The Indienpanzer project and its failure is mentioned briefly, together with a statement that at the time German industry was incapable of developing a modern MBT, that the failed India project gave German industry and especially Porsche the knowledge needed to make Leopard 1 work.
I don't have my reference material here, but vaguely recall another abandoned German tank development project for a south American country from the 1980s, a cheaper, smaller, alternative to Leopard 2 (and a competitor to the AMX-40 which was being developed by the French for the export market). Maybe that's the one you're looking for?