Yeah, they are indeed but it can never hurt with a little less mass to lug around. In fact, my friends factory stock 62' Plymouth Savoy Max Wedge might as well be an A body since its real all steel carcass only weighs in at 3395 Lbs wet at the curb.
Imagine if I had started a weight loss with that chassis instead of my mid-life whale 3600+ Lbs.