"Soon" DL will have updated and reconfigured all of their international 767-300s into the staggered flat beds in BE. However, the A330 is used on the ATL-EZE route for part of the year, and while modifications seem to be progressing quickly, only a few of these aircraft have been done so far.

DL tends to fly more flat beds--and generally better aircraft--into Brazil, so connecting into EZE using SkyTeam partner AR might work to get flat beds most of the way, especially if one doesn't need to obtain a visa from Brazil to do so. Another option might be to connect through Chile, depending on one's situation with respect to their reciprocity fee.