Well at least you got a Mustang, you got the heaviest and slowest one ever made in GT form except your exact car with an AOD. You're not making enough power to worry about touching your suspension or brakes. You need a good shifter first off, then you need a set of 4.10 gears, thats 1/2 sec. in the 1/4 mile right there. Subframe connectors if you're gonna run sticky tires at the track. Do a tune up, with synthetics and a K&N and good plugs, take it to the track, if you have stickey tires launch it at 6000 rpm and powershift it at 6000 and you'll be surprised how fast you can make it go. The next thing I'd do is nitrous but you may not be ready for that yet and if you have the money get a good blower or turbo kit.

Good luck,
Briane