If the rear end is original, it should be 3.42:1 (RPO "GU6". If it's a posi you should see "G80").
The ratio and other info can be found on the RPO sticker, provided the gear ratio wasn't changed. The RPO code sticker is usually located in the center console on the passenger side wall. Sometimes it's under the hatch.
A list of what the codes mean is HERE