My late gunsmith and friend, Harry Creighton, built a .458 on a military Mauser and it worked perfectly. The same was true of the .458 he built for me on a Springfield action. The Springfields and Enfields with their slightly longer magazines are perhaps easier to convert. Or if you really want to simplify things, I believe I have a pre-64 Winchester Model 70 action marked .458, which would only require fitting a barrel.