1. Put the back of the car up on jackstands ...

2. go under the car and put a chalk mark on the driveshaft.

3. Have someone turn the wheels one full rotation and count how many times the driveshaft turns while your still under the car.

If the driveshaft makes approx. 3.5 turns you have a 3.42 ... if it makes about 3.25 turns you have 3.23s, etc. etc.

If you have 3.42s definately spend your money somewhere else ... 3.42 is plenty of gearing to get the lt1 going, very nice low end power.