how to identify stock rear springs

[bigchap]

Hi i have been looking into replacing my stock rear springs because my ti is starting to have bad body roll in the back and it is riding with the rear wheel arches almost on the tires. The original springs have almost 148,000 miles on them, so i figure it may be time, plus i drive it like i stole it. I have been looking at rock auto to see what it would cost but it shows three or four different types of springs, ( inconsistent wire diameter, consistent wire diameter, k flex, heavy duty). I need to retain the original ride height or maybe a little higher, i drive alot of gravel and occasionally it turns to mud so i need to ride height. If anyone can explain how to identify what type of spring i need or help me figure out what will fit my car it would be greatly apreciated.