Luke
I have a No1 in 45/70 and I have shot a 458 No1 a fair amount.
I think a 470 No1 might be a little stout on the recoil end for comfortable shooting.

Actually since the No1 handles rimless rounds so well it is hard to beat a 458 Win Mag or a 458 Lott, as there are so many cheap bullets to be found.

For pure hunting purposes with a bit of nostalga a 450/400 3" would be hard to beat.

But then again,in a No1 a 416 Rem Mag is a lot cheaper to shoot and you can duplicate and surpass a 450/400 if you think it necessary.