What are your guesses?
Under 6 seconds?

 

I don't think the changes will make much of a 0-60 difference.

2003 G35c/5AT/BS-Graphite/Prem/Aero/Splash/NISMO sway bars/JWT Popcharger/Z-Tube

 

ya...i think the current stock best time is around 5.5.....i am guessing 5.4 the fastest for 05

 

Assuming that the weight remains the same, 15 hp at the crank should increase 0-60 times by 0.3 seconds.
http://www.cars-cars-cars.org/0-60-Times-Calculator.htm

2003.5 G35C 5AT
Premium Package
Tire/Wheel Package
K&N Filter, Z-Tube, EGK

 

that should say DECREASE

2003.5 G35C 5AT
Premium Package
Tire/Wheel Package
K&N Filter, Z-Tube, EGK

 

So now the question is if the 19" wheels are going to be light enough to off-set the acceleration penalty for the larger diameter where essentially less torque is making it's way to the ground.

Future G35C Owner... ...Never too soon to think about modifications!!

 

Would the closer gear ratio make a difference in 0-60 time?

 

It may make a difference if 3rd gear is likewise lowered and you can keep traction. But you may get get a drop off at high end.

2003.5 G35C 5AT
Premium Package
Tire/Wheel Package
K&N Filter, Z-Tube, EGK

 

KAHBOOM - Great sig. vid.! Pretty long too. lol

'05 IP(or ?) 6MT... ...Never too soon to think about modifications!!