So did the modified springs help out ,I'm still trying to decide if it's worth doing them.
1] are you going to tow?
2] are your rear stock springs shot? (Mine probably were not, certainly in better shape than the fronts)
3] what are you trying to improve? see #1. If you plan to tow, I'd say upgrade the springs at LEAST to the B codes, and do a sway bar, no matter what!!! But I'm not a towing guy, talk to those guys.
4] I AM a guy who used to modify one, and only one car (the 1990-1996 300zx) about 100 different ways, with 90 different customers, over a 2 year period. I did get a chance to try a bunch of stuff, and figure out what was changing things for the better, by starting out with the cheap parts first, and then going to the more expensive. From reading everyone's Ford posts on the subject; not just Stewart on FTE or Cary, but as many posts as I could find, I found a common thread, and also compared it to my own experience with the 300ZX. Some 300ZXs came with a rear sway, and some did not. The ones that came with no rear sway sucked at handling, and simply adding one made them a different car.
It's the old Hot Rod addage: you spend 10% of the money to fix 90% of the problems, and the final 90% of the money to fix the last 10% of the problems.
My vote: sway bar first. What did it "fix"? it made much better the straight line feel on the highway, and I KNOW it must have helped the wind-gusts steering the truck around. I did not get a chance to experience gusts before the mod, but I have, in the last month, driven it from San Jose to Sacramento (the Benecia area), and LA (over 152, extreme gusts) and been thru some extremely gusty areas and it handles it as well, or better than my 4800lb BMW 7 series, which is also a good bit smaller and lower.
On my Excursion the FIRST thing I did was the rear sway. I loved it, even with dead front springs, and Gcode rears. I can say, that I then did the dead front springs, and drove that for a week, and loved it just fine, and then modifed (my way) the very decent rear G-code springs I had to B-codes, and still say, the rear sway was the biggest deal.
That is my take-away from this job. If I bought another Ex, and I was on a budget, sway bar is the first thing I would do.
If money were no object, I would follow Cary's advice and get some wider-than- stock, 18" or larger rims, for road use, and get off those 16x8 x32" balloon tires for long trips.
I am not there, yet.