I don't know how much you have in your altered carbine, but if it isn't much, you ought to think about selling it to a collector who knows what parts are needed and has access to them.
They will be expensive.
Properly brought back to original configuration, the carbine will never be worth what it would be if it still had its original parts.
Its basically just a documented 1st US cavalry receiver. Thats something that will net you some profit.