You will need to ship that gun to Les
www.diamondgunsmithing.com, or someone of equivalent experience, knowledge AND HAS THE PART to get that gun fixed. I went and looked at it on Armslist. It is missing the barrel lug that is silver soldered to the barrel.
Les has parts, you should ask him.
Also keep in mind, Ithaca DS barrels of that era were tight. You would not want to accidently run a sabot down that barrel.
Could it be a nice gun, oh yeah, for the price. It could also be turned into a really nice turkey gun.
Have Les fix it, ream the barrel and tap for choke tubes. Instant turkey gun.
You might even be able to find one of the screw in external tubes that has rifling and use it for deer.