For Larry, Nick or anyone else that has dealt with these units. The 5831 Pencil Gear map Larry sent me measures .309" at the tip. My 5531 housing measures .369". Did you notice if your tail housing has a bushing pressed in? I've located a drive gear (pn: 55-452-6) and sent the rest of the information to Stewart Warner to match up the pencil gear. The drive gear is said to be for a 5831 but matches my 5531 tail shaft and blank dimensions. On with the hunt....
EDIT: Added picture.