Infect was always a solid sleeper pick for Modern. Recently, Tom Ross has shown us the power of Become Immense in the archetype, albeit in Legacy. I think it's worth investigating in Modern, and apparently so does the Gatormage.
In order to fuel it, he went with a solid G/B shell featuring four copies of Grisly Salvage. While a little slow, it does help you find an Infect creature and fills the graveyard for Become Immense. Gitaxian Probe also works quite well here, since it's another card to put in your graveyard for free, and it gives you valuable information, which is always helpful when you're trying to combo your opponent out.
The sideboard is simplistic, but I don't mind that with this archetype. You shouldn't be trying to do anything fancy, and you don't want to oversideboard in basically any matchup.