I have a 96 wagon and it has a 13mm rear sway bar. I know some say the 18mm gen 1 will fit the gen 3 with no issues. I have never seen one so I can't say too much abut it. However I do know the back of the muffler on the dual exhaust Duratec comes very close the the existing sway bar. I would be concerned that it may scrape the muffler it it is not precise.
I have been looking for a gen 1 wagon in the bone yards since I have heard this and can not find any.
If anyone has done this on a dual exhaust I would be interested to know how it went and how did it effect the ride?