The barrel would need to be set back in order to use the 450NE because of the thinner rim. The rechamber to 450 AKN. would be very cost effective. I used a 458 WM barrel to make my 450 NE Ruger #1 because of the hefty tube on the 458. The 450 NE will 'just' clean up the 458 chamber.

There just happens to be a new Pacnor 50X18 twist #5 contour available at AR for $250 right now if you decide on this route.