We did this job on my 86Turbo, but as far as I know, it can't be done on the '90+ because of the differences in the harness and ECU programming.
I'm sure someone knows about this subject more than I do... Good luck, Diego.

 

Yes it can be done! But first you new a service manual! The wiring diagrams will show you witch wires you need to redo for your speed sensor, neutral switch etc. I did it and have no problems. Make sure that you get the right parts na parts for na ect. Dont forget the drive shaft the auto shaft wont work. You will also need to get the manual starter harness. It goes from the main harness to the manual trany. Thats were the manual comes in handy the number of pins in this plug is different that the auto plug you will need a depinning tool so that you can redo the plug from the auto starter harness. Good luck!

 

I forgot to tell you, since the nissan ecu's are stupid( they run on a 8 bit system) you can change the tranny and run the auto ecu IT works! Also if you leave all the boxes for the the auto in you can keep your cruise controll!