Hi.
You have a few considerations that means that the typical examples
do not fully apply to your car.
1) You have a heavy vert. So, the car will sit lower on a given set of springs.
2) The extra weight means that the car has more kinetic energy as it goes over a bump. So, you need heavy springs.
3) YOU HAVE A FOUR EYE with VERY LITTLE fender/tire clearance. Many people with a 92/93 just can't seem to be able to comprehend that "for some reason" Ford didn't keep the Mustang exactly in all aspects since '64!
4) You can lower a pre-86. But, many people that BRAG about their lowered 4-eye seem to often forget to tell about the REQUIRED mods or tradeoffs! Most people will roll the fenders (which *I* will
not do on
my car), push out the front fender bottom support, and/or run some
POS tire that has it's width over stated!
5) The rack of a car can be very personal. For some people, they are very picky about the rake. If you're that type, then IMHO you have
ONE good/proper option - get the MM adj rear arms. At ~$400+, there aren't cheap. But, IMHO, every other rear adj arm is a POS and I don't think that cars that have them should even be allowed on public streets.
6) To be honest, and looking at it from a mechanical engineering point of view, you have limited options for a vert. Every option will result in a harsher ride.
7) If you don't have subframes on the car, then you MUST get them before you put on heavier springs. The notch is a POS design that has the stiffness of a wet noodle. The hatch (most typical) is worse. And the verts have the stiffness of jello.

So, people that put on stiffer springs without first welding on subframes end up with a car that handles like cr*p and is twisting itself to ruin.
8) IMHO, your best bet is to go with a similar setup to what I have. If you live in a area with good roads (a myth in New England

), then you might want to go with the Bullitt springs and the Steeda spacers up front. In the back, Bullitt springs and MM adj rear arms. The Bullitt springs will be
roughly 0.2" -> 0.3" lower.
9) Mods can make a huge difference!
Alum heads remove weight from the front. A 3-core radiator (like I have) adds weight because of the added water. Etc.
10) Do NOT believe the PURE AND TOTAL BS that all tires of a given size (ex: 245/45/17) have the same height, or width, or tread patch, or will clear a wheel well the same. Just check out the specs on tirerack. My 245/45/17's have one of the widest tread patches of a tire that size. That's why I went with them. That also means that I have
less fender clearance than a "typical 245/45/17".
Good Luck!