That sure seems like it would be a long jump to the rifling from 45LC to 460, and reaming from 45LC to 454 Casull doesn't seem to hurt accuracy, and in fact in mine it improved the 45LC, so I would be hesitant that I might ruin it by going to 460.
I feel the same as CW when it comes to easy to get brass, and less expense, then you throw in the time tested fact that the 45-70 is probably the most versatile of the big bores, it's pretty much a no brainer, unless you just have to have a 460 just to say you do.