Thanks for asking our advice
Dick Casull, when working up loads and producing his first guns was using 45 Colt brass (modern stuff, not the antique "balloon head" cases used for Black Powder, and which have not been manufactured for over a half-century anyway).
So, yes the brass will stand up to the "Ruger Only" loads and the gun (chambered as it is for 454 Casull) will stand even higher pressure.
However, if you choose to go past the "Ruger Only" loads, your gun will hold up. The brass almost certainly will hold up. The primers, however, may not. That's why Casull brass uses rifle primers.
Go forth and be happy.