Unless the rifle is an antique that you don't want to externally modify, or it has sentimental value, I'd recommend just rebarreling it with a newer high-quality blank like a Bartlein, Brux, Rock Creek, Proof Research, Christensen Arms, Schneider, Krieger, etc... If it is an antique or sentimental, I honestly don't know who does re-boring. Maybe you'd be able to talk to one of the manufacturers that I listed and tell them your situation, and they might be willing to help you out with your project.