Umm no... You are so incredibly incorrect I just lost faith in the world. Im going to just let you reflect on what you just said

if you bought coil over's off ebay for $40 that say they are universal ( which I don't recommend anyways coil-overs are crap ) they are designed to fit on almost anything. a lot of springs are almost all identical from one brand of vehicle, so lets say you get all gm's if they have a similar suspension setup its almost garunteed the springs are the same

Uhh no grand prix springs are different they might look the same but they have different tensile strengths