David -
I would say don't reuse it as is. You could see if a machine shop could repair it by turning it down and making a press on sleeve of the right size. However, after the bill from the shop you might have already paid for a new one. From your local Chevy dealer the input shaft should run around $350-400. It is a replacable part as my dealer told me he could get it if I needed it. Also, try calling the place you got the rebuild kit from in case they can get parts like that.
Frank