Years ago one of the magazines had an article on some of the tricks: light battery hidden under stock-looking case, gutted seats & gutted equipment like radios, heaters, etc. And then moving weight like filled spare tires.
I'm sure the guys didn't spill all the beans, but a lot of stuff can be duplicated in aluminum - all it takes is time & money.
I know a guy that made a lightweight steering column - he put a lot of work into it - but it weighed maybe 5 lbs complete.