Should you decide to return the status of your gun to DR, relining the rt barrel would require some extra care. Ideally you would need to match, as close as possible, the dimensions, twist and rifling of the left barrel. Also, you'll need to chamber cast the Snider chamber and have a custom reamer ground lest you end up requiring different ammo for each barrel. Jim Dubell would be my choice for this work. He makes special cutters, when required, to match groove width, and so forth. Doubtless, others are out there who could also help you. Jim's number is 509-684-5855.
Otto