Looking into upgrading rear suspension

I'm still looking for ideas. I'd like to get new springs since the ones on my car now are the stock /6 car springs.

Anyone use the Mancini XHD a-body springs?

I'd think about SS springs but I don't want the car to sit that high from looking at Adam's B'cuda. But while browsing magnumhp.com I saw some billet lowering blocks so they could be used to lower the rear a little but I don't know if that's a good idea that it will work against the SS springs or if they won't hold up on a mostly street driven car.

Anyone have any advice or suggestions.