Unfortunately if you want the factory nav system you have to get a Z that has it already.
Up until recently it was thought the same thing about going from factory nav to aftermarket but that was proven wrong. (
DIY - Nav System Conversion) My Z has the factory nav and I hate it. I’m deleting my factory nav later this year. I would suggest going with a nice aftermarket system if you want navigation in your Z.
Now I’m not saying its impossible putting the factory nav into a non-nav car. I took a quick look at the service manual to see what would have to be done. In my estimation the time, effort, and money it would take would cost a lot more than a really nice after market system (not exaggerating one bit).