"LX Only"

That kit is basically a Saleen Ground Effects kit.

The reason it's LX only is because GT's already have ground effects.

You could put it on a GT, but you'll need to convert the GT to an LX first by swapping the front and rear bumers, removing the side skirts and changing the door moldings.
 
Yes, LX door moldings.

They stick on with double stick tape and a could pins so it's easy to remove the GT door molding and install the LX peice.

You will also need LX moldings for the front fenders (before and after the wheel) and the rear quarter (before and after the wheel)

Basically you are replacing all the moldings with LX peices. The GT moldings are attached to the factory ground effects kit so they come off when you remove the GFX.

Like i said, you gotta convert the car to an LX body first.