Wbulk Wayne sounds good. Go easy on the T-5 trans, they don't take alot of abuse. This is a sound drivetrain for NORMAL driving. If you get bitten by the MORE POWER BUG, you will already have a good rearend to start with. The gear ratio may change depending on what the ratios of the trans are. Alot of guys have started with 3.50 gears and gone to either 3.70-4.10 gears.
With the overdrive transmission. What is 5th gear ratio in your T-5 trans? You might want to start with a 3.90 ratio. The problem is that the motor is not a big one or have a ton of torque. Torque is what moves your car not HP. You want your car to cruise easy in the power band of the motor which is about 2,250rpms. If you cruise at too low of an rpm the motor lugs and burns more gas. It also will not pass as well and you will be downshifting more than you want. Have to also remember that you are driving a barn door down the road, not a bullet. The CD of drag is not the greatest with cobras.
Rick Lake Ps I run 3.31 gears with a 1-1 five speed, a ton of torque at 482 cubes. This is a nice all around setup for a cobra. First gear is too quick with a 3.15 ratio for the trans in first. Going to a 2.80. Rick L.