Get him a new stock, here is one for a good price. http://cgi.ebay.com/Winchester-model-100-Carbine-Stock-Un-Issued_W0QQitemZ250228976405QQihZ015QQcategoryZ739 49QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Don't get much easier than that, just swap um out, and if your sneeky maybe you can switch them without him knowing making for a big suprize for Grampa.