You can find just about anything you want for the car with the exception of the side molding. If the molding on your car is good protect it with your life. I've looked everywhere for it and haven't found any in the entire country. I have used all the parts retailers in the country and have found Texas Mustang and 50 Resto to be good but as far as finding OEM parts CJ Pony is the best (In my opinion)
http://www.cjponyparts.com/.
As far as mods go I would look into gears and exhaust first. If you have a 5 spd, most likely you have 2.73 gears. A set of 3.55's of 3.73's will really wake it up. The weak link in your car will be the 7.5 rear end. Its why Ford put the 8.8 in the GT the following year. Try not to spend much money on the 7.5. It would make much more sense to find a used 8.8 and throw that in then to rebuild the weak 7.5. I'm one of those "old guys" that is the original owner of my 85, and even though I have babied it I had to replace the 7.5 twice before I woke up and gutted a used 8.8 and put that in last summer. If you have any question about the car feel free to IM me.