A few years ago when I was looking for a 5-speed transmission for my 1976 280Z project, I searched and searched for photos of the early ("wide ratio") and later ("close ratio") versions side-by-side. I never really found any, but I did acquire one of each, and thought I'd post pictures of them for easy comparison. The main things to notice are all on the rear extension housing:
The wide ratio gearbox has two exhaust hanger ears on the rear extension housing, the close ratio has only one (on the driver's side).
The wide ratio has a dust collar/shroud surrounding the end of the tail piece, the close ratio does not.
The close ratio box has a cover for the reverse loickout mechanism on the left side, the wide ratio does not.
On the close ratio, the screw that secures the speedometer drive assembly to the rear extension housing is located at 6 o'clock (toward the bottom of the transmission), on the wide ratio the screw is at 12 o'clock (toward the top).
The striking rod guide (where the shift lever attaches) is slightly wider/taller on the close ratio than on the wide ratio.
Overall, the wide ratio rear extension housing has s smoother, more rounded appearance.