I'm pretty sure the 73's weighed more than the 72's. People were becoming more safety conscious in the mid 70's and nothing is safer than Mass in a collision. I'll take mass over airbags or "crumple zones" anyday. A "5 star" Honda civic head on with a "1 Star" Z71 Silverado club cab, everyone dies in the Honda, no scratches to the occupants of the Silverado
I would have loved to modify an S3 or Can Am back when they were cheap. I had opportunities to buy them, but when NOBODY is drag racing them or autocrossing them, even though they'll easily take a big motor and the suspension is the basically the same as the earlier cars, something has to be up. Mass is that something.