Have a look at upgrading to an R34 3/4 synchro/sliding hub setup, they use solid type key.
D22 navara's also use some of the same gear just under different numbers, but it is hit and miss with the models
A basic tell tale on auto condition is the colour and smell of the oil. You're actually meant to service autos every 12 months 20000kms to maintain them well.
The turbo boxes can be built strong you've just got to do it right