While I don't have experience with 4500 carbs, I recently went from a downleg 830 to an annular 1000 HP 4150. Right out of the box with only jetting and idle mixture adjustments, my 451 ran noticably crisper on the street with better throttle response and gained 2 tenths at the track.

It's notable that I changed the fuel delivery system at the same time, going from 5/16 to 1/2 line, and adding an auxiliary electric pump.