I am discovering the same issue. The GP outer tie rods are vastly different from the (true) A-body cars. which is just about the only significant steering and suspension part that is really different. The Center links and inner tie rods are the same. So is the idler arm, pitman arm, and steering box. The outer tie rod ends for the GP are very expensive(well over 150 each), and I guess I will just have to bite the bullet and buy them.
https://www.rareparts.com/RP25500A-2...iac-Grand-Prix OR
https://www.kanter.com/products/stee...d5301243390cb7