All of my Mountain Guns wear the older factory Combat Grips.
The top two are chambered for 45 Long Colt while the bottom two are chambered in 41 Magnum.
This is my favorite grips for the N-frame revolvers with round butts. However as they become harder to find I have gone other routes.
I really like Hogues newer grips for the round butts. They fill the hand better then the stuff of a few decades ago. This Tulipwood example is on a 610 not a Mountain Gun, but you get the idea