Well, actually over time, springs tend to wear out, and the prior owner could have overloaded the car, causing rear end sag. I had an '83 Nissan Maxima that would drag its tail. Replaced springs and struts, and the tail end lifted up giving muscle car look like you described. I eneded up replacing the front as well, and the car leveled out, and man was the handling improved. The '83 was rear drive with IRS.