I was the first to install the 7/6k swifts on the BC's and love them, far better than the springs they came with and all linear instead of linear and progressive.
The last time I weighed the car it was 2575lbs and with the standard springs, two big dogs, wife, a bit of luggage, it would bottom out on big overpass bumps, etc.
It rides better, handles better and never bottoms out now
Rick