Tongo ,

I know this reply is a bit late for your thread . I took a Ruger #1 in 458 Lott and did exactly what you wanted . The cost was that of the chamber reamer in 450 3 1/2 express . The belt on the 458 Lott is smaller in diameter than the base of the 450NE . The Ruger extractor is spring loaded from the side so it does adjust to the different rim diameters including that of the 450 . The only other slight modifications were to remove a small amount of metal from the top of the breech block slightly to clear the rim for extraction and to remove the breech end of the sliding safety to also clear the rim during extraction . I did the conversion with the stainless steel tropical and had to polish the chamber but I would venture the regular steel would cut easier with the reamer . It shoots very well and functions flawlessly , and is the type of project you could do at home with simple tools if you were inclined . It took about 3 hours to dismount the barrel , cut and polish the chamber , breech block , and safety slide and reassemble . Recoil is very tolerable . Jim