You could aways grab your old springs & cut 1.5 coils off. Thats what I did yrs ago when I had FRPP's K/W springs The rear sat up higher, so I took 1.5 coils out of the oem springs w/ no issues. It doesn't hurt the springs from a material stand point. I saw a couple of pix w/ Dom's arms= In one the perchs were down & in another the perchs were sitting higher. As far as RS springs, I guess they are similiar to svt's. So I'd say any lowering spring would be shorter.
Introduce Mr. Torsen to the mix
Bigger brakes then you- D23 crew- D-Tech- Sedan Revolution= #131