Ok, you made me curious. :D
So, I went out and took a look at my SS springs. I was running the 460/461 SS springs, which are for a 3600 lb car. Yikes. Not sure what I was thinking, my Challenger isn't that heavy. Anyway, my Challenger rode like a truck with those on it, but I couldn't bear to toss them completely so I'm using them as placeholders on my '71 Dart.
Now, my Dart is currently without engine or transmission. Everything else is still on the car, the front is on jackstands (so there's more weight on the rear) and there's a set of slot mags in the trunk just for good measure. This is what my shackles look like. Not quite vertical, but still plenty of room to move.