While I'm not a Nissan / Infiniti expert, I believe the FX, G35, and 350z use the FM (front midship) platform meaning the engine is behind the front wheels. The Maxima, Altima, Murano, and Quest use a front wheel drive variation on the FM platform.

Technically the FM platform makes the cars a mid-engine. Unlike the mid-engine Acura NSX, or Toyota MR2, the engine is mounted in the front rather than the rear. The advantage is that this package can achieve an almost 50/50 weight distribution, in the case of the G35, 53% front 47% rear, giving the car more neutral handling.