I don’t have a car at the moment, but I used to own a Pontiac when I lived in America. I also had a Ford Puma, but since I didn’t need it much in London, I sold it.
The only modification to a car I had was increasing the ride-height by ~15cm for going off-road in the desert. That was a Renault 5. I didn’t do it myself, but I think it just involved tightening up the torsion springs.