Spring experts, quick question.

Go with your OEM rear spring. Rear spring rates are all very close. Most rear springs are the same rate. If you want, go with the MM adj rear spring perch to adjust height. Or, get an MM rear lower with the adj spring perch.

Get stock springs at the junk yard, ebay, classifieds, etc.
No reason to go to an adj rear perch if you just want stock height! Go with a stock spring. In fact, a stock rear spring will be a little higher because you have a lowered front-end. But, I'm *guessing* the stock rear spring with a lowered front spring will lift the rear by an additional ~1/8" higher than with the stock front springs? Not much, but for squeezing in rear tires, every little bit helps.

That's because the CG (Center of Gravity) of the car is moved a little forward with the lowered front. That puts a little less weight in the rear.

So, you'll get more of a rake, which I like, and more rear tire clearance.

Also, going with a stiffer rear shock will help prevent the rear from dipping too much on bad roads, bumps, potholes, etc.

could you double or triple the rubber isolators on the rear springs for some clearance? just a thought

85-98 Mustang V8 springs are all the same. If you don't want to get new springs for the back, just get some MegaBite Jr's spring isolators. Each isolator is hard plastic and they lift up the car 1/4".