1987 5.0 Mustang

[84LX89GT]

If you felt like having it ride smoother but still handle stable you could try putting in 4 cylinder mustang springs. They're fairly soft, and i believe that the '93 Cobras came with the 4 cylinder springs and front strut cartriges (at least that's what it says in one of my mustang books) to have an easier more daily driving type feel to it. The 4 cylinder cars themselves have no rear sway bar, those soft springs and soft struts/shocks and a tiny front sway bar so they wallow all over the place.
I had an '83 zephyr (same as a fairmont.....originator of the mustang's "fox" chassis) and it had the stock springs (soft like a 2.3L mustang), but 5.0 mustang struts (pre '87 so it would fit the spindles) and rear shocks, mustang rear sway bar and stock front sway bar. That thing handled really well and have a very tame ride. The springs really soaked up bumps well and the stiffer control from the rear sway bar and struts/shocks made it feel really predictable and safe to drive (unlike the way it was stock).
The best thing is used 2.3L springs cost hardly anything (you can easily find some for $100 or less for all 4 springs at any wrecking yard) and compared to other alternatives and can actually ride like a luxury sports sedan instead of a pure sports car.
one thing that you may not like about the 4 cylinder springs is that i've heard that the front may sit 1/2" to maybe even 1" lower than stock, but that shouldn't have any serious impact on the wheel camber.

I hope you find a solution to your problem, keep us updated!