My friend, Andrew Larson, and I were looking to swap out our final drive gears and finally did it. 3.69 to help him enter his powerband earlier for drifting and 3.54 to lengthen the shift points of the 370z.
Much to everyone's advice against it saying it wouldn't net any noticeable difference...
We've found out otherwise. 
The swap went extremely well and have found out that a 3.54 in a 370z, makes the car feel like it's a much smoother accelerating ride and still can pack a punch if you put it in it's powerband. I'll be updating this post with the speeds I reach for high speed cruising.
5th Gear:
2500RPM = 55 MPH
3000RPM = 65 MPH
3500RPM = 75 MPH
6th Gear:
2500RPM = 68 MPH
3000RPM = 82 MPH
3500RPM = MPH << Still waiting for that time when I could test this now... 
Negatives:
Cruise Control is no longer working. Not a problem since my foot still works. 
Honorable Mentions:
Andrew Larson: For your hardwork and the 350z Final Drive
IntecRacing: For the use of your facilities and all the help you provide during my project.
I'll be more than happy to update the original post if any questions come up that everyone should benefit from.