Raising the rear end

I had air shocks AND shackles in my first high school '65. I dont know WTF but when I went over speed bumps and the suspension rebounded, it made a hell of a lot of noise locking the shocks up, like someone hitting the floorpan with a 3 lb sledge. My shocks were probably the wrong size, bought it like that so it would not rub the 10" wide wheels in the back on the fender trim. Scared passengers...bump..."WTH was that!!!" haahahaa