Putting the GT grill on the other models will unfortunately mean swapping the whole bumper (as grill area is one piece with bumper). Probably better looking to get it wrapped/customised.
The handle is held on by one visible screw and most likely another similar screw behind the door card. You’ll need a matching piece of black trim to replace it, but definitely doable. Some say the handle will be removed for J1 (from a Ford source but not sure I trust it).
probably to get around exactly this -US style sequential (even if amber) not legal in EU -brake light needs to be more visible when used together with indicator