I have several Mosins. My technique for mods is to buy a duplicate part from one of the major parts houses, take off the original "matching" part, store it in a safe, well-marked place, and then modify the replacement part. You can then return the rifle to its original state by swapping the old part back into place.
I've done this with front sights, a stock, and one cocking piece.
I like a pull ring on a Mosin safety. To fabricate mine, I bought a dog leash swivel at Home Depot, cut off the clip part, and used the D-shaped ring with a circular base to mount onto the cocking piece. I had to file a bevel into the circular base to fit the sloping surface of the cocking piece. The hole in the center of the circular base still allows access to the screw slot so you can adjust the firing pin depth. Mine is attached with two screws and JB Weld epoxy. It works fine.