Troll the F Body forums. I did when we classed the car in R and it can make weight based on what I learned from people pulling parts off them for drag racing. HVAC is a lot of weight, as is the exhaust, seats, etc. Window glass is a lot of weight too, very large, and large GM style power assemblies too. Gut both doors and lose that stuff. Rear seats and fold down assembly was something like 50lbs all told.
They might be a good R car. The motor can make more power and there are a lot of suspension goodies available for them. And they are cheap cars to buy into as well, cheap to maintain for parts.
R