Honestly, here is my 3 cents on the matter. First ask yourself, what am I wanting achieve from this car? Speed....looks......how much money do I want to spend. I've had a modified V6 for quite a few years, and of course I have a V8 now. Now I'm not one of those guys that are going to bash you and tell you "Get a V8" because I find that a ridiculous remark that doesn't help squat, but this is what I'd do.
If you are thinking I don't care to have a ton of power nor do I want to spend much cash my thoughts.
-Find some 17 or 18" wheels to your liking (you can find good set off GT's and Cobras for cheap)
-Lowering springs with maybe caster/camber plates (FRPP makes a line for cheap)
-Bolt on Dual exhaust kit (directly bolts to the ypipe, MAC and Flowmaster make one along with some others)
At this point you have a good looking stang with alittle rumble for not too much cash. Don't bother with a GT Bumper unless you find a really good deal on one.Really all you need to have for a V6 Stang IMO.
You want more than just that than do this.
-T-lok in the rearend, with 3.73's and uprgraded axles
-Short throw shifter, shift kit/tranny cooler and high stall converter if auto
-Underdrive pullies, TB and Intake spacer, K&N air filter and a hand held tuner
More than that (one of these most likely)
-Camshaft
-Blower (supercharger/Turbo)
-Nitrous