I went to a junk yard in Iowa City, Iowa on new year’s eve and measured the mounts for the independent rear suspension on a 1997 Mercury Cougar. Oddly enough, I think it will work well. There are 4 mounts to the IRS and the two back ones line right up on my frame rails. The front mounts are not far off, I will just need to build a mounting block that I can weld to my frame rails and bolt the IRS front mounts to it. This IRS setup is also missing both calipers and a spindle from the drivers side. I located those already and have them on the way.
The wheel bolt pattern is also different, so I will need to change that. The width of the Cougar rear end is 63 inches wide from hub to hub, and I think the width of the Stealth’s rear end is somewhere around 65 inches. (I haven’t measured exactly for the Stealth) As long as the Stealth rear end is about 65 inches wide, by using 1 inch thick adapters on both wheels, I will be able to convert it to the right bolt pattern and have the correct wheel spacing. Depending on how things go, I may also just switch spindles for one from a 99 Mustang Cobra and use RWD spaced wheels.
Pictures are below of the new IRS and the initial fit to the car. From what I can tell, I will need to fabricate the front mounts to be around 4 to 6 inches tall. The support beam between the two frame rails also may be slightly in the way and hitting the top of the IRS frame. If it is going to be in the way, I will need to either drill the spot welds and move it about an inch towards the front, or cut notches in the beam and put another support beam to the front of it.
(click image to make bigger)