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

I know a stroker B engine with aluminum heads, intake, water pump, and headers can weigh almost 100 pounds lighter than a small block.

I have always thought that the first fiberglass parts to put on were the front and rear bumper. I know steel bumpers weight alot. I just wonder exactly how streetable that is at a grocery store parking lot.