I think that gun would be interesting, the Ruger #1 in a .458Win would be brutal in recoil...without some modification.
I agree 100%.
As originally chambered, the #1 in .458 already needed the - not one but two - mercury tube recoil dampeners installed.
The .450 No2 Nitro is about identical in ballistics at the muzzle and down range but with not much over half the chamber pressure.
Due to this lower pressure, the recoil is slower but from the Ruger #1, it is still too painful for most of us mere mortals.
As issued in .458, the #1 is muzzle heavy anyway so, mercury tubes in the butt stock not only adds to the badly needed weight deficit but also balances the rifle up quite well.
He also installed either a 1 inch Pachmayer Decelerator or a Kickease recoil pad which, is way superior to that red colored scrap of truck tire Ruger puts on them.