correct, the stock bolt on the rig is too small in diameter for use without adding a sleeve inside the bushing on the shock itself. that is all. i got mine from home depot, plumbing part.. never had a problem since. you could possibly take the sleeve out of the stock shock and re-use it but when i tried with little to no tools it was more work than it was worth.
i will say though that the crown vic shock, in my opinion now is not long enough. i will go and compare it the the fj60 landcruiser shock for length, i want another inch but no more. my brake lines, particularly the parking brake are maxed out and i will require some adjusting there, should be minimal.
it seems that when my rig is on a hoist the front wheels travel down further than the rears now with the bds extensions up front, not good as i want the rear to work harder than the front.