I would go with the largest throttle body offered. air flow shouldn't be your limiting factor. its important in a carb only to get the fuel flowing out of the bowls. in an efi system, the injectors fire no matter what so don't limit your HP potential and get a small throttle body. also you have a 496, I don't know if I would run a dominator on there at 2000 cfm if you want to drive it on the street. you could even get away with a 1200cfm version. any larger than that and part throttle driveability will suffer.
It is possible to go too big with EFI just like you can on a carbed engine.
When I moved the turbo 440 from a factory Cobra throttle body to the 1600 cfm Accufab I felt a distinct loss of throttle response.
