Here is what i did to mine, involves stretching the roof with a 2nd roof section while i was at it i replaced the little 48 rear window with a full size 51 rear window. this was the end result Good luck on your chop, take your time and measure three times!
Here is one owned by a guy in the Cherry City Bombers Car Club..Pretty cool truck. http://www.facebook.com/home.php?sk=lf#!/photo.php?pid=9657688&id=308948260345&ref=fbx_album