I bought my 2nd G35 a 2006AWD sedan used with 24,000 miles on it.
When I went to replace the brake pads they were a different size.
The stock pads I bought were ~1/2" smaller in length than the one's on there now. I verified this with an another autoparts store and they are the correct pads for the front brakes for the make, model and year of this car.
How do I determine what pads I need? Is it possible the original owner ordered upgraded brakes direct from the dealer?

 

Take your old pads to the parts store and shove them into the salesman's face. Then ask him to get you the right pads for the car.