The system at porto is irrelevant. His role was to finish off the chances created for him. They had other players playing between the lines, providing close support and linking the play. It's also far easier physically to play as a single central striker in Portugal than it is in the Premier League.
For what it's worth i think he'd probably form a great partnership with Van Persie. The two would compliment each other very well. My worry would be what happens when Van Persie is rested or injured. I dont see Falcao having much joy as a lone central striker in our current system, in our league, his game just isn't suited to it. And i dont think our other forwards-Chamakh and Walcott-would make great partners for him. And I dont think we'd get anything by playing him from a wide position.