The 11-12's don't use the GT500 tophats. I bought them, and they aren't compatible. I did get an adjustable panhard bar though. Everything else was aligned within spec.
Sorry to bump an old thread, but I'm looking to buy these too. All you did were springs and panhard bar? No shocks or struts? I read somewhere these springs (I think on americanmuscle) that these frpp springs required something for the newer 11-12's gts for a proper install
That's what I was informed of too. They told me I needed GT500 tophats. It's not true. If you go aftermarket struts, then you need the aftermarket tophats.