Hi Guys

My 383 R/T 71 chally needs a carb change, as I believe the wrong one might be on. It purrs great and responds extremely well to throttle movement, and burns rubber well. But as the rpm starts getting over 3000, it tends to choke, so to speak, and the pull is not there anymore.
Since I have owned this car, I have not touched it yet and my mechanic believes it may have a small carb.
That being the case, what carb should I get for it (obviously after checking everything that might lead to such a problem)?
What should there be as an original equipment, and is there a better carb to fit to it than what originally came on such a car?

Thanks