Yep weight factor and taller gearing up front helped good old Ford avoid the tax. Sadly the ZL1 weighed too much and because of this the engineers had to do lower gearing up front to get the performance figures they wanted (i.e. 0-60 mph, 1/4 mile) to be competitive with the rest of the market. Hopefully the next generation Camaro (2015 maybe?) will be on par with Ford in the weight department
But I will be super impressed with the New GT500 if it avoids the GG tax because with all the ZR1's supercharged glory (similar HP/Torque figures to new GT500) and a more efficient LS9 motor (compared to LSA), they still couldn't avoid the tax :(