Yes, there is a good online site for your question. Check your rear axle code on the tube and then check this site:
http://www.chevellestuff.com/index.htm
Go to generic info, then click on axle codes/ratios. You will need to crawl under your car on the passenger side and look for the code on the front side of the axle tube. Then compare it to the code on the link above. My LS5 car with M22 has the CRV code which is 3:31.