Before you quote a post from almost 11 years ago, do yourself a favor and click on the user's name. That will take you to their profile page, which shows you when they last logged in on this site. In the case of JSR, it was back in 2012, so it's highly unlikely that you're going to get a reply from them.
As for what rear end to use, it would help to know what car you're working on. You've bumped an 11-year-old thread in the 1st gen CTS-V forum, but your username implies that you're working on a 2nd gen CTS. If that's the case, then asking someone with a 1st gen CTS-V what rear end you should use is pointless, because it's not the same as your 2nd gen CTS.
