As far as I know, if you're staying with the same airline and passing through Ezeiza, you won't need to reclaim your baggage or pass through customs - the customs is literally the last stop on your way out the front door of the airport, just before the taxi stand, so it wouldn't make a lot of sense. You should be able to just follow signs for "Pasajeros Transitos", in-transit passengers, and stay within the international terminal, and go straight to your gate. If not, also, it would be pretty much impossible to make your connection, getting through Migraciones and Customs in under an hour at Ezeiza... not.