if you are talking about a newer 5.7 or 6.1 Hemi in I hope you can do your own work. Otherwise it will be very expensive and won't run even w/ a mild 440.
For somebody like me w/ limited skills I'd stroke the 440, or maybe supercharge it. Pretty easy ti make 600hp with a 440. Not sure how much work it would take to make a 5.7 turn out those numbers...and don't forget about torque. It depends on your wallet and what you want out of the car.