I'm not one of the 'prefferred guys' (HP2, Chryco come to mind) on suspension but I'll give you my opinion anyways.
With your ball joints and bushings, using the Moog offset uca bushings would be a good idea.
I have the Edelbrock IAS shocks and like them, $80 each from Mancini's, But there are a lot of choices out there depending on your budget.
If you don't have already, subframe connectors. Doesn't have to be expensive if you build your own.
Higher rate torsion bars (if you have stock now) will improve your handling, as will a set of sway bars.
As for your sagging rear end (talking about the car right?), it looks fine in your signature pics. The rear wheel on a stock Challenger is supposed to be somewhat tucked up into the wheel well. You shouldn't see the top of the tire when you look at it from the side. But if you prefer the raised in the back look, ESPO is used by quite a few people on this board. I use Mopar XHD springs @ stock height, with ESPO you can specify how much over stock you want.