The folded mirrors came on the 04 Special 40th Anniversary v6's/GT's and the 03/04 Cobras...they are very nice, but pricey, and will need to be painted unless you can find a pair in your color already.
You could get some silver/chrome mustang letter inserts for the rear bumper. Or a chrome fuel door...always a nice accent to the wheels.
A Mach 1 chin spoiler really dresses up the front and compliments the grille delete. The front end really looks unfinished and junky if you look at the car straight on...that damn radiator guard is hanging down and the bumper sits too high. I'd consider one.
If you have 99-04 and have the hood with the small forward facing scoop you could get a 01-04 GT hood scoop. Find a used one already painted or buy a new one for 150 and have it painted...same deal with some side scoops from the 01-04 GT's. I recently picked up a pair with attaching clips in perfect condition for $120.
12 Black GT500 SVT PP l VMP TVS l JLT123 l O/R X l 28x11.50Rx15 M/T Street R's l BMR Suspension l Recaros
03 Sonic Blue 3.8 / 17 Magnetic Fusion Sport 2.7 EB