The bolt face will work for the 375Ruger. If you're bound and determined to go 458 WinMag, a rebarrel, #5 taper and new magazine box may be needed. You'll then have to widen the rails for the fatter cartridge. Shouldn't be hard for the two cartridges mentioned.
-------------------- Lo do they call to me,
They bid me take my place among
them in the Halls of Valhalla,
Where the brave may live forever.