i had the same problem with my 92 two door. i replaced the shocks in the back and it was like i had no suspension at all. i had 2" spacers all around, so i replaced them again with crown vic shocks, cheapest ones i could find, made a huge difference, also the tire pressure. I ran around 20psi on 30x9.5 and rode great. i also noticed that when i disconnected the front sway bar, it also rode nicer, going over speed bumps and stuff.
but yeah, little things can make the ride really harsh with these.