Go here
http://www.nicoclub.com/FSM
Then compare your MY G35 to the 05/06. You should be able to track down how the two systems differ.
I'm assuming that the fan on your G is thermostat controlled as well, but instead of it sending electricity to operate the fan, it send electricity to operate the clutch.
Worse case scenario is that you'll have to replace everything from the clutch onwards. Best case is that you can rewire the thermostat directly to the electric fans (not likely).
There is also a company called Flex-a-lite that makes low profile fans and they may be able to help you out with the project.
Last option is to call EverythingG35 and talk to Joe OR call Riverside Infiniti and Talk to Tony.