I would see how it shoots before wasting time and money putting another barrel on it. Take it out of the stock, clean it up really well. Find a mount that fits the tapped holes and stick a scope on it and have fun. Even with mismatched numbers it might surprise you and be a good shooter! Have fun. If it shoots well, maybe spray it with Duracoat or something. It looks like in one of the pictures it may have had some kind of paint on it already that is coming off (pic of barrel near the receiver). It isn't a parts gun, just an old Mauser that someone sporterized.
"Where Zen ends, asskicking begins" - Hyde - That 70's Show