I'd hesitate and do a bit more research. The .454 Casull runs at pretty high pressures when speaking of max hunting loads. The "proof" loads are at astronomical pressure levels.
Not many of the Elite Group of "Top Gunsmiths" will bother with the .454.
The lowly old .45 Colt cartridge will work quite well.
I'd recommend reading what Ross Seyfried has written on the subject. One of his articles is posted on the web. Click HERE
John Linebaugh is one 'smith whom has been "at the roots" of these LARGE CALIBRE Single Action Revolvers. He has some very informative
info posted on his website. Link to Linebaugh's site HERE
. His "Writings" section contains lots of good stuff.
Ruger has indeed made a .454 Casull Super Blackhawk prototype. The story I heard is that the recoil was unmanageable. Obviously Ruger didn't use the Bisley grip frame.......
As Usual, JMHO,