FWIW: here's what NHRA listed as minimum weights back in the day...[all weights are for 396/375hp w/4-speed]
<u>300 Deluxe</u>
Coupe, 2dr: 3157.5
Coupe, 2dr: (Sport): 3198.75
<u>Malibu</u>
Coupe, 2dr: (Sport): 3221.25
Those weights are supposed to be from the manufacturers, but are typically light, but I'd say they're all *relative*...so, 75 difference from lightest to heaviest.
[There was a '69 Chevelle 300D that ran in Pure Stock a couple years ago...350/300hp/automatic...that car only weighed low 3400s with the owner in the car, and he was probably in the 200 lb. neighborhood. Car went 12.8s or 12.9s @ 106+, iirc...]
So, whatcha buildin'....