If the other barrels come with the gun you describe, I would think the package would be worth $1,000 and more. You just are not going to find double rifle barrels in .54, and that .10 gauge set makes a whole other shotgun, if it fits.
The metal work on the guns is good enough to justify spending money to buy a newer, and better figured stock, if you are not happy with the one on it. If ou contact Dick Greensides, at Pecatonica, he can use the existing stock to make a new one with whatever grade of wood choose. He also can length the stock a bit, so You can decide if you want a recoil pad, or simply obtain a metal buttplate from Track of the Wolf, or other suppliers, to put on the gun. Pedersoli might even supply a buttplate for the gun.
My CVA kit shotgun was way too short for me, so I added a recoil pad to add the length needed to the stock. The drop at the comb was not enough, so I removed wood to get it to point correctly for me. The wood on the gun is plain jane something- probably birch or ash. I am thinking of having Dick Greensides make a new stock for me, so I can dispense with the recoil pad. While it makes my gun distinctive, it does not fit with that period of gun. A proper American Walnut stock, with a metal buttplate is what it needs.