Looking for some advice on a suspension package for my 08 GT/CS. I recently switched to the 2010 SVT 18" wheels, but at 9.5" I am worried about tire rub if I lower it. The wheel gap is pretty bad and I really want to get rid of it.
You won't have a problem. They are the correct offset and I run Roush 18 x 10 wheels with no problems. You probably don't want to run anything much wider than 275 width tires on the front, I think 305 width tires even fit on the back without any problems. I haven't heard of anyone with rubbing problems from those wheels.
Eibach makes good quality equipment. I have a set of UPR/Eibach Pro Kit springs waiting to go on my car, and the Eibach swaybars are soon to follow... but the Sportline springs (progressive rate) are more of a cosmetic improvement rather than handling improvement. They're low enough to adversely affect your handling.