A Factory Ride with A Pro Kit from Eibach

[drudis]

Stock ratio on my 1989 was similar(?) to your rates, in that they were progressive 430#-550#.
My first set of springs was the EIbach, with a 450-580# rate (most every single company out there makes these). This, in my opinion, is how the factory should deliver these cars. Nicely lowered and nice sport rate springs.

If you want more, then I went with the 650# BBK linear rates. These were fairly stiff, and not all too recommended for a daily driver.
I wanted more track performance, and went with 425# coilovers (about 1600# rate for comparison). Now THESE are not a friendly street spring.

YOU need to decide from here on what you are going to get. IMOHO, 10% you'll barely notice firmness. 100% increase is entry level track springs at 900# and up.\