3.73 are bad for 1/2 miles
Why would a 3.73 rear gear be bad for a 1/2 mile? If you're running stock 3.31 gears you will be required to shift into 4th gear by 135mph, and with a 3.73 you'll just be shifting into 4th a bit earlier, albeit the rpms will drop less during the 3-4 shift keeping the car in a more optimum power band.
Just curious why you said they're not good for 1/2 miles?