First, the Model 11 is oneheckovagun. Like it's A5 cousin, it lasts longer than a bad reputation and works under any conditions.
Turning this into a SBS kinda bothers me, and not just because I'm not a SBS fan. This especially applies if it was owned and operated by anyone who contributed DNA to your personal gene pool. IOW, a family gun. It's an heirloom, not a opportunity.
These are GREAT shooters.
If you shorten that stock extensively, the recoil spring and carrier doodad will punch a neat hole in your shoulder. Take the stock off and you'll see.
That ring bulge probably comes from firing off a steel load in a barrel not built for steel shot. A flagon of mead says the ring is right where the choke taper starts.
In your shoes, I'd....
Get a set of new friction rings and springs and install them. This rebuilds almost all old 11s so they can be used with modern loads.
Have a decent smith cut the barrel right behind the ring and install a bead sight.
Next, you can decide to have this as a Cylinder bore gun, accepting the limits of range and pattern. Or, you can have the smith install choke tubes, and have a much more versatile shotgun.
NOTE:
Long recoil actions that have the barrel bobbed way back tend to batter the internals. A certain amount of weight is needed in the barrel to keep things in balance.
HTH....