[84LX89GT]

You're lucky there's a whole bunch of options to modify your car. You name it, you can do it. Just ask questions according to what you want.

Now to make your car sound better, there are exhaust systems that you can buy that convert it from a single exhaust pipe to dual exhaust pipes with larger piping and freer flowing mufflers, etc. The advantage of this is 1. The sound is deeper and loudness depends on the muffler you get and if or how many catalytic converters there is in the exhaust (stock on your car i believe has 3, 2 before when they come together and 1 right after they join). this will give you the roar sound you want
and 2. you'll get better gas mileage and more power because the engine isn't trying to push the exhaust out, instead it's pulling itself out (i won't discuss exhaust scavenging or temperature/pressure waves...little too complicated for a beginner)
There are kits to convert your car to GT/Cobra exhaust which sounds nice and is fairly quiet. But if you want your car to roar a really popular exhaust manufacturer is Flowmaster. You can find flowmaster at http://www.flowmastermufflers.com/web10/indexf5.html
They have sound clips as well, and you can email them and ask them about a shop nearby that does exhaust or you can ask them where you can buy it to do it yourself.
also a company called MAC makes lots of V6 exhaust options:
http://www.macperformance.com/macsto...atemustang.asp
You can contact them as well about shops that will do work or just to buy it yourself. Chances are if you buy exhaust that is street legal (has catalytic converters in the "H-pipe") any shop will install it for you and most are fairly easy to install so there's not a whole lot of shop time involved.
Good luck,