I would do nothing more than remove the scope and mount, then fit a slide into the rear sight base and experience what the original owner felt when firing it for the first time. The 1-14" twist is odd but I would trust that old Harry knew what he was doing and at least give him the benefit of the doubt. I would think it would stabilize a 150gr bullet ok. Maybe a cast bullet at a sedate velocity. What form does the rifling take, what is the condition of the rifling and what grade steel was used are the questions I would ask before deciding what kind of load to put through it. But fire it I would.