Following up on Toddd's observations:
The shocks on my car are (still) Edelbrock, which are built "inverted"--they have to mount that way to work properly, due to the internal release valve/port that is part of the design.
Bilsteins for the B-body are not built the same way internally, and while there is no specific reason for the position they mount now that I am aware of, with the shock body attached to the lower mount, it is possible, with some assistance from Bilstein, for the rear shocks to be inverted so that the shaft/piston is affixed to the lower (axle) mount. I would guess that the shocks mount as they do to give the piston shaft some protection from being struck by an object that might come up from the road surface.
Back to Cheston's basic issue of reducing weight, specifically unsprung, there is a ratio of weight spread for the moving elements of the car--the entire rear sway bar is not 100% unsprung, for example since it mounts to a part (the LCA) that is attached to the frame. I don't know the calculations to figure it out--maybe Eric Bryant can help. The use of lighter wheels is probably the one area you can make a bigger gain that anywhere else, at least on the rear. Front would be by going to a brake system with aluminum caliper, and, ideally, a 2-piece rotor with aluminum hat. Baer uses aluminum billet hubs for their B-body brakes, so there is another gain. The only other way to make serious inroads in this area is to go to a tubular control arm setup or by figuring a way to adapt Corvette forged alumninum suspension parts, which I would be concerned are not up to the task of supporting the weight of the car and its suspension loads.
I also think its wrong to assume that our cars MUST have a rear sway bar--if the front geometry could be made right, I opine that a rear bar could be eliminated. I'll say no more on this for now, but I'm working on something.....my lips are sealed for now.
As far as the "truck arm" Todd mentioned, I ran across an ad and website for a shop here in SoCal that advertises just such a setup. This is not an endorsement, and some may be offended or otherwise dislike the name and/or what you see at the site, but here goes:
A truck arm system would necessarily need a panhard rod or Watts link. So far I have not been in touch with these people, so I do not know if what they offer could be made to work on the B-body. They are doing a setup for early Chevelles, so the similarity suggests to me that it COULD be done. All it takes is money, I'm sure....