Can I upgrade the gears without buying a whole new rear end in my 2005 gto. I changed the cam to the cheater thunder racing cam and used the afr 205 heads and Im getting only 429 rwhp and only 385 lbs of torque. It seems like Im not getting to the power as the peak hp comes at 6250 rpms but drops like a cliff at 6500. The motor has been tuned by a well known gm tuner in my area and I miss my torque at the stoplight but it does throw me back at 4000rpms.My peak torque is at 5200 rpm. I have a 6 speed does anyone have a recommended gear to use for this powerband? I used to own a 2002 corvette but I couldnt change the gears without replacing the whole unit which was over $2500 plus install.