Well I'm not sure about the suspension kits, but I have Ford lowering springs in my 1990 mustang gt. You will loose a noticeable amount of ride quality with lowering springs. Lowering it will help the handling and it looks a little more aggressive, but it will ride like a go cart. When I bought my 1990 the shocks were worn out, so I figured while I was replacing those, I would replace with new springs to lower it (and when I say shocks were worn out I pushed the strut rod in and it didn't come out). Anyways the car felt better after everything was done, up until I bought my 1988 mustang that has stock suspension and good shocks...that was the tell tell story right there, that lowering it made it ride really rough. If I had it to do over again I think I would look at keeping the stock spring and trying to find drop spindles to put on, this way you lower the car on the front, without loosing ride quality.
Also I wouldn't lower the car more than 1 and a 1/2 inches in front, more than that can have serious issues on alignment. I dropped mine an inch and a half on the front...now i have to stack boards on top of each other to drive the car on the boards to get it up on the car ramps to do an oil change.
You will also occasionally scrape your h or x pipes on speed bumps after you lower your car, and you will have to watch out for that concrete stop that they put at the end of some parking spaces as some are high enough that they will break you front bumper.
Steep dips in the road are also a nussance along with intersections that dip down and then up as you will inevitably scrape the front bumper after it is lowered.
I didn't look to see where you live, but if you live near Ocala, FL; I'd let you take my two cars for a spin to see if you really wanted to drop it. If this car is your daily driver...then seriously reconsider. If the car is not your daily driver then it will definitely help the handling, but be about 2-3 times rougher than it already is.
1990 Mustang GT with AOD transmission-quite a bit done to it. First mustang I had, & still have.
2003 Mustang GT-Total lost by a friend into a golf course. RIP GREY GHOST
2002 Dodge Ram Quad Cab 4.7liter, auto transmission, towing package
1988 Mustang GT convertible with manual transmission- BONE STOCK! New IAC (because it idled at 2500 rpm)
1990 Mustang GT Convertible with AOD transmission project car & building it for a friend