They're pretty much for cars that are lowered, and therefore are beyond the adjustable limits of a standard alignment machine. I suppose there are probably other circumstances too, but lowered is the main one you hear. It depends on the drop of the springs really, and I'm not familiar with the springs you are going to put on yours.
but c springs only lower like 1 1/8 in the front and 7/8 in th rear... i don't want to spend money if you haven't figured it out yet... will i run into any really bad stuff?