You know, you could use a larger carb if you wanted to. However, a small carb is not always a bad way to go. You'll get snappy throttle response and you've got enough air to turn it past 5000 anyway.
Remember that the factory 396-325 horse engine had a 585 Holley from the factory. They ran very well with that carburetor. It's better to err on the small side than the large side.