How much weight can you shave off of an A-Body...and still have it look/drive like an A-Body?

Depends on where your starting. Here is a couple of easy mods......
1). If you go from power to manual steering, that's 40 pounds. Plus, it frees up a lot of room under the hood (hoses, pump, brackets, belt, bigger box). Also, you can loose another couple of pounds off the crank if your replacing a 4 groove factory crank pulley with a single groove.
2). If you have the 5 mph shock bumpers, you can remove about 35 lbs per bumper as there is a lot to remove behind the bumpers (and still keep the steel bumper). 70 lbs easily lost between the two.....
3). Of course, aluminum intakes and wheels is a sure weight loss....
4). Power to manual brakes will free up more room under the hood and shed about another 5 lbs
5). If ya have the fold down rear seat, certainly some opportunities there......