The South American attack conundrum is a bit tricky, I think it's useful if we can express what we they they all were best at in terms of roles and qualities and make sure of as less overlap as possible. I'll try to list the qualities in the order of their impact on said player's greatness as all these could basically do everything.
Lionel Messi : RW/CF. Dribbler, Finisher, Playmaker.
Diego Maradona : AM. Playmaker, Dribbler.
Pelé : SS/ST. Finisher, Dribbler.
Alfredo Di Stefano : CM/AM/ST. Finisher, Playmaker, Defender
Ronaldo : ST. Dribbler, Finisher.
Zico : AM. Playmaker, Finisher.
Garrincha : RW. Dribbler.
So that's the spread as far as I can say. The top three there all bring three different key assets to the team as their primary qualities, so all of them will play. Needless to say, positionally there's zero overlap and you'd have Messi (RW), Maradona (AM), Pelé (ST). It's a direct competition between Pelé and Fenomeno as they bring much to the same, so Ronaldo drops out. Now comes the trickiest one in the mix : Di Stefano. The only way he can be a part of the team is if we play a 5 pronged attack, and even then, both him and Maradona would have to play the left inside forward role, as both played on the left side of the pitch. There's actually no way whatsoever to include Di Stefano unless you replace one of Diego or Pelé, which isn't happening. So that would be another exclusion. There's no space for Zico either, and Garrincha can feature given we go with the 5 up front tactic. So first attempt could be:
Pelé
Rivelino - Maradona - Messi
OR
Neymar - Pelé - Garrincha
Maradona - Messi
I'll go with the second. I went for Neymar as he's the best South American LWF of all time, as well as his telepathic chemistry with Leo. He wouldn't interfere in the playmaking aspect unlike Rivelino or Ronaldinho would and would be a fantastic outlet on that flank.
Coming to midfield, and I wouldn't count Di Stefano as a midfielder, his best was clearly as a CF no matter how complete he was. Leaves us with some decent decisions to make. Given we are going with a 3-2-5, we need strong midfielders who can sit deep and dictate play, we cannot include the likes of Didi or Gerson as they would foray forward a lot and that is counter productive. There's little room for the Uruguayan Varela as well, in this formation. It comes down to three names for me : Fernando Redondo, Paulo Roberto Falcão and Jose Leandro Andrade for those roles. If this was a 2-3-5, Andrade would be the first name on the team sheet. But in this case, I'll prefer the Argentine and the Brazilian.
Lastly, in defense, the central figure is undisputed. Greatest South American defender of all time: Don Elias Figueroa. For the left back, Nilton Santos would be a shoe in. The right back is trickier. I had a tough time deciding between Javier Zanetti and Carlos Alberto, while Pupi's influence in midfield from the right back position is invaluable, it's Alberto's staunch defensive ability as well as his ability to tuck in centrally (you'd rarely need an attacking output from a RB with Garrincha on that side, he'd hate you for making him share his space), he got the nod.
Shocking lack of depth in the keepers pool, and to represent the two time World Champions, I'll include Ladislao Mazurkiewicz. My final team:
This is the best I can do while creating a 'fantasy' team. Sure there's still plenty of talking points like which one of Messi or Garrincha carries the ball on the right or whether Diego pulls the strings or Leo? But I'd let those dilemmas be a part of this, at the cost of a bit of realism and retaining the fantasy element to it.