If it was made before 1987, they probably won't but it won't hurt to ask. I've thought about cutting a dovetail and making one for the rifles, but as Slufoot said, not for a shotgun barrel. One thing you could do for the shotgun barrel would be to make a saddle of sheet metal, use a short piece of ¼-20 or ¼-28 screw to attach the stud to the saddle, then silver solder or epoxy it to the barrel, even tho there wouldn't be much engagement for the threads, once it's attached to the barrel, it would hold fine. Then just relieve the forend to fit the new stud mount.
Tim