Cervini's Rear Bumper

https://www.cervinis.com/product.aspx?car=1&id=1122#311

I've been checking out possible idea's for replacing my GT rear bumper and found one on Cervini's that looks really close to a Saleen rear valance. It's middle of the page, part number 4302. It looks good and it's cheaper than the 93 Cobra so I made up my mind that I want it, but it says in the description it's for "LX Only". Anyone have it on their GT or know why it wouldn't fit a GT?
 
It attaches the actual LX bumper, which is what the Saleen kit did in the first place if I'm not mistaken. Either way, that's what the Cervini's (and all the other companies that make the same LX-only piece) is all about.