In theory, going to a 3 link/TA setup with yield a very noticeable improvement in ride quality.
When experimenting with the PM3L, I found that the ride with H&R sport springs and bilstien shocks was vastly better than before the PM3L. Hence, that's a good place to start. Lots of compliance in the suspension but still pretty well dampened (rolled like nuts though, stiffer springs are recommended). Staying with all rubber bushing and such will help in that endeavor, but handling and performance will suffer accordingly. Since handling is a priority for you, you'd probably want to stick to urethane, IMO. Harsher but totally worth it.
I should note that while it is possible to get by with the PM3L and have it work pretty well, it is by no means ideal, and even with a good deal of work to get it to work for a while, the floorpan will give out after a while (few years maybe) anyways. I tried it with stock style control arms and wasted a lot of money doing it.
Another must have is subframe connectors. Anything to make the body more rigid will help. There are arguments if a strut tower brace has any real effect in the foxbody since the cowl isn't exactly strong compared to the actual strut towers, but I've heard some say it helps NVH. If you have a hatchback, you might also consider putting a rear strut brace, but I've basically never seen anything on people using one so not sure if it would be worth the trouble. A guy at the autox's has one in his hatchback Merkur, and he says it was basically pointless.
And while it hurts performance of the car, ADDING weight will at least academically, help ride quality. Increasing the ratio of sprung weight (you want more) vs unsprung weight (you want less) will yield a more compliant ride. Taking weight out of the sprung weight will also help (lighter suspension components and such, which is why modern high performance cars have a lot of aluminum suspension components). Lighter wheels and tires will also help a great, great deal, since big wheels and certain tires are very heavy. Name brands are the way to go for wheels, since Chinese knockoffs are usually heavy as a boat anchor.
Sound deadening will be your friend here also, since it adds sprung weight and removes noise. I'm no expert on the subject but I know you need sound blocking foam in addition to sound deadener for maximum effect. Opinions vary on brands and methods, so doing some research is a good idea.
I've no idea what to do to the front suspension. I've never ridden in a foxbody with an aftermarket k member/control arms.
From what I've read the S197 chassis is lightyears better in every way than the Foxbody. It's based on a Lincoln LS which was a rebadged Jaguar, so ride comfort was obviously a high priority in it's design, whereas the foxbody was designed in the late 70s to be a family sedan/wagon and was only okay when it was new. 20-30 years on, with minimal changes to the design over the life of it, the chassis is going to need quite a bit of work to be made comparable to a more modern car.
1989 Mustang GT: 5.0, 5spd --- Sold. SVO brakes, MM suspension bits, 331ci, X pipe.
2012 Mustang V6PP 6spd MT --- Daily Driver, D Stock auto crosser, maybe track days some time...
Last edited by That89GTGuy; 09-28-2011 at 05:10 PM.