Dont know about "incredible" Heinz because every car was much lighter in those days. They were smaller for a start. They werent cluttered up with things like air bags. They had much smaller engines with much less power and that in turn meant lighter gearboxes, drive shafts etc.
Interestingly, manufacturers at last are aiming to reduce weight. McLaren is an example of someone following the Chapman mantra. Lotus always have tried to do so.
