If that is a M1899 carbine with a 22-inch barrel (proper front sight and crown), and the M1901 sight has the proper "C" markings, the only thing wrong is the cut-down rifle barrel.
Replacing the stock will cost approximately $300, M1899 carbines go for $1000-$1200, sometimes more.
M1901 Carbine sights can cost $200 or so, so if the sight is wrong, figure that in.