I haven't purchased one, yet, but it would be a .44 Mag., as I intend to use it for deer hunting.
Perfect, go with the SBH Bisley hunter. It's easily available in .44 mag comes with the Ruger mount all integral to the bbl and includes the rings. Add your choice of a scope and you're all set. Simple as that.
For something a bit different, they did offer these albeit in limited quanities in .41 mag and even fewer in 45 Colt. the later may become available again this year but that's not definate.
Changing gripframes involves removing the grips, the hammer spring assembly and removing 5 screws that hold the gripframe onto the cylinder frame. Reverse the order and you've Bisleyized it. Changing the trigegr and hamemr just add two steps (removing a pin each) and again reversing the order toreassemble.
Be easier to go with the Bisley hunter from the get go though.