On the newer Marlin Guide guns and Outfitters you can pull off the buttstock. On the left side of the gun,in back of the cross bolt safety,there is a small set screw that screws in towards the front. It has some red plastic stuff on it which appears to be thread semi locker.
It is easily unscrewed. Back it out. Push the cross bolt to FIRE. Install some BLUE LocTite. Re-tighten screw. Crossbolt safety will not move. --- SAWMAN
I did the same Beartooth Mercantile thing on a blued 1894 and a stainless 1895 w/o the saddle ring. Looks like a screw on both sides. I would recommend for both function and appearance plus easy install. It's the way Marlins should be made i.e. w/o manual safety. But for under $20 per and it turned out great it was worth it to me.