Red lights rule! Nothing wrong with rice (actually, started as "euro", then got appropriated by the nipponese manufacturers, who actually put them on as oe equipment - lexus, nissan, honda, etc.) - on rice. The oe tail lights on your 03 vert are gorgeous as is, and match the angles of the body. Changing them to some imitation of a lexus layout just adds a dissonant chorde to the Mustang's graphic design chorus.
If you just have to change the rear of your vert (I have an 02, and I like it just as it is), removing the vestigial wing (also known as "bullitizing") and doing a professional paint job on the repaired trunk lid would be an idea...
But leave the poor tail lights alone - all that clear lenses and fake chrome is way tooooo much.
"You can never be free until you let yourself go."