Did anyone ever install the paddle shifters in a 2005 G35, either with a wiring mod or different harness or otherwise?

 

Works Bell makes a fairly easy to install kit, and supposedly people have installed OEM paddles onto G35 sedan/coupes without the option. That being said, it requires some custom fabrication for the OEM paddles (I think the mounting point is different behind the wheel), while the Bell kit require a few minutes of dremeling/a few holes to drill and is fairly plug and play.

You could do it from scratch, all you'd need to do is essentially extend the switches/wires under the shifter and provide a way to send a signal from the wheel.

 

Yes a friend used the Works Bell kit in his M35 Stagea (basically the same dash). They are an amazing looking set of paddles - not cheap though!