I too want to be able to drive my car on the street without problems and having to unhook one side of an anti roll bar. This is what I purchased from JEGS. It fits the 68-72 chevelle, etc... but should fit our G-bodies as well. I haven't put it on yet but it should work well. This bar also is a MAJOR imrovement over the stock rear bar. It's also very reasonably priced. Granted it won't work as well as a Spohn bar or the ATR bar but it's a very good comprimise that will bolt right on with no mods! Good luck!!
http://www.jegs.com/i/Suspension+Techniques/876/51050/10002/-1
http://www.jegs.com/i/Suspension+Techniques/876/51050/10002/-1