You can do it without too much trouble. The simplest way is to use a Bearcat stirrup, another hammer strut, and a new mainspring (maybe not the mainspring, but if you do you'll have it available). The Bearcat stirrup can slide and possibly fall off of the stirrup perch (or whatever it's called) so some slight filing to create a place for the new stirrup to sit. I hope that made sense.
My shooting partner and I did it to a Lipsey's 44 Special or a 357 midframe he has. Can't really remember which one. It works fine and has never caused any problems.
If you're adventurous and capable, the better way is to make a stirrup to fit the perch.