be weary the stumpy on an R30 is very different to the 720 navarra or d21

The R30 has shorter lever position so is more suitable to most datsuns
while the 720 is a 71C box with different shifter and length.

The navs get quite a pounding and usually have overheated main shafts that
weaken over time also with lack of oil changes.

Either way you are most likely up for a rebuild with any of the boxes mentioned
as they are getting long in the tooth