I have a 1994 Mercury Marquis (85k) with the front tires leaning. I also had a 1993 Ford Crown Victoria (214k) with the same symptoms.
When I put a floor jack under the A-frame and try to move the wheel back & forth, I don't see any movement from the ball joints. The A-frame bushings are solid. The outer tie rod ends are brand new, but the front tires still lean in, and the tires wear quickly (20k), but evenly (no cupping).
Anyone have any ideas as to whether the upper or lower ball joints are bad (or both)??