Like headers they (manufactures) no longer make parts unique to a specific car body. They sell a product that fits pick-ups Chevelles, Camaro's, and all GM full size cars. This way they make one product with one claim and get you the experienced mechanic figure out how to install it.
It is easy to claim something in an ad, and they point to their satisfied customer list (have you ever seen a bad review?) to move product. Once you pay for it it's your problem. That is today's business world. There is a reason other companies charge more for a product and you hear good things about them on this board and others (not paid for reviews).