I have 275/40/18 tires on my '97, and the quad shock I found that fit behind the wheel was a Motorcraft F4ZC-4A489-AB equivilent (sp), found it at Autozone but they have it listed as a steering damper, so it was hard to find.
I changed the pass. side this morning, need to see about the other side #s to see if it's the same.
Taking the original replacement shock and turning it around still didn't fit the car, so I had to find the smaller quad shock.
On the box it said it was a 4 hour job to replace two of them, but with a little WD-40 it took about 15 minutes to replace one.