Also on seating the bullet out -- I run 350gr Barnes TSX bullets to the max length that will fit in the magazine box which gives me case capacity for Lott-sized powder charges. At that length I still have plenty of room in the throat and leade. Works very well. Same general practice should work for you to get a 'bigger case' out of the 458Win in your Ruger #1 with whatever bullet you choose.
I crimp.

Cheers
Tinker