The .416 Remington and .416 Rigby are basically identical, the Rem was made to duplicate the Rigby but I hear there are pressure problems with the Rem. The .458 Lott recoils more than the .458Win. Ruger do not make Left Hand rifles in the calibres you are after also Winchester only make a .375H&H (unless you want a Custom Shop rifle) Ruger make all of these in the No. 1 single shot.
RLI