why not get a Ruger No 1. in 458Lott. then you can shoot from 300-600grain.
the smallest i shoot is 350grain, and it look kinda small in the shell hehe.

i havent had the pleasure hunting with it yet, but i am pretty sure the things i hit turns up dead. the most importent is that you handle recoil and get plenty of practice.

i would say a 300grain from a 405win is the same as 375h&H with a 300grain,

here is a picture, of a 350-400-550grain in 458 lott