You know if I were you, before you "pull the trigger" and lay out a bunch of cash for something that might or might not work for your particular application, I would read Mark Savitske's book. How To Make Your Muscle Car Handle. The book is only around twenty dollars on Amazon. Mark dedicates a complete chapter on Springs, Rates, and Shocks.
According to Mark, there are several things to consider before installing Coil-Over Shocks. The main thing is you need to install new shock mounting points, or reinforce original points, because the coil-over shock eliminates your coil spring, which was carrying the load of your car. Your original shock mounting points where never intended to take the load of the car, along with the rear suspensions travel cycles that a coil-over shock will put on them. You also lose some suspension travel because the coil- over spring is shorter in length than your original coil spring.
You should do some reading over at, pro-touring.com There are a lot of guys over there running coil-over shocks. Most have pro touring / autocross setups under their cars with a lot of other parts and mods to make those coil-overs work properly.
If this is the direction you are going with your car I think some good bilstein shocks, would be a good place to start for now. Spend your money on other areas of the suspension that will improve steering geometry and handling first. Unless you have already done that.
Just my .02
By they way, I am not indorsing Mark's book, but no one can deny that when it comes to the A-body's suspension, Mark knows his stuff. I have been studying up on the A-bodies suspension and gathering parts for a long time in order to be prepared for my build. There is a lot of misinformation as well as parts that won't help your suspension, but will actually make things worse. Mark's book will make it clear what you need to do in order to achieve your desired goals.
Hope this helps, and Good Luck!