Analyze My Timeslip

Dumb question. How does a 67 dart weigh even remotely close to 3800 pounds.? It appears to not have a cage/ rollbar?
Reason i ask, my all steel 69 Dart with rollbar, Full carpeted interior, etc, etc missing only the back seat, weighs 3310 with a full tank of fuel and my 320 pound butt in it...lol
Not sure if this helps any, but your Dart seems pretty light, and OP's dart seems heavy. For frame of reference, my 67 Barracuda is 3250 with my 175 pound self in it (no heater box, no carpet, glass hood, has roll bar + frame connectors).