Yeah, your next step will have to be to remove the diff cover and locate the ratio on the ring gear. Just rotate the gear until you find the small engraving. Then just convert the fraction to a decimal to see if you have a 3.364, 3.545, 3.90, etc. You'll have to know this before shopping for a LSD.
While doing that, take the opportunity to clean the area inside and out, then get some good synthetic gear oil to refill the diff.
- Greg -