Will take a look for the SVO video, they are the reason the car is staying 2.3. Glad to hear that the FIT system works well, coming back to the Mustang scene after so many years their name wasnt familiar to me - other than the movie of course.
What do you suggest for springs, have the stock 2.3 NA, the Turbo Coupe and the Ford Motorsport 5300 springs new in box or something completely different? Had thought about coilovers but dont see the need to adjust a street car so not really seeing the need
I always try to give the most accurate information, so forgive me for the long reply...
In all transparency, I didn't know much about the 2.3L Mustangs when I started my 2.3L project. I had a lot of experience with V8 Fox and SN95 Mustangs and there was a lot of aftermarket support for V6 SN95 Mustangs when I built my "Mustang ST" a few years ago. While many
suspension parts for 5.0 and 2.3L Mustangs are interchangeable, there are some key differences. This carries over into the aftermarket, which ignores the 2.3L when it comes to some parts. Aftermarket 2.3L-specific springs are rare. For this reason (and others), I plan on using coilovers on my 2.3L autocross car. But it's worth mentioning that I don't use coilovers on my other cars and they handle pretty well. I don't think you need to use coilovers for your build, but I do think you will have to do some experimenting.
I experimented with lowering springs when I installed my UPR K-member. I installed a pair of new 99/01 Cobra
Eibach Pro-Kit front springs (progressive) that I had left over from a previous build. Later, I installed a set of Ford Performance M-5300-C rear springs. I've driven the car on the street with those springs installed and the ride feels pretty good (not too stiff, not too soft). The ride height (at the center of the fender lip) is 26.75" F and 28" rear. The rake isn't ideal, and I prefer my autocross cars to sit at about 27" all around. Keep in mind that this car's interior has been gutted during the build, so it's probably close to 2,500 lbs. There isn't a lot of weight over the rear end.
Ford Performance 5300 "C" (linear) and "B" (progressive) springs are listed for V8 cars. I've seen other forum posts where people have used them on 4-cylinder Fox Body Mustangs. If you have a set on hand, it might be worth trying them. But you'd have to be willing to do all that work again if they don't feel right on the car. Which version do you have?
I don't know enough about the Turbo Coupe spring rates to comment on whether or not they will work.
Eibach does make a set of progressive springs designed for 4-cylinder, Turbo and SVO Fox Body Mustangs. Part# 3518.140. They are progressive rate (better for a street car). They lower the front 1.2", so you might want to use poly spring isolators to raise them up a little for better handling. I've never personally used these springs, but the fact that they are 2.3L specific when others aren't makes me think they're a good option. Because these springs fit a wide variety of models, you might also want to have some Steeda spring spacers on hand.
I hope that info helps.