Good luck
and
CHECK MY SIG DAWG
Personally 67/68 fastback is my favorite mustang. Buuuuuut they cost about as much as your DD.
A restored coupe will be little under or around 15k. Of course buying restored takes all the fun out of it IMO.
If you're looking for a project to beat on and fix up with your spare change I would go with an unrestored coupe with your preferred body style and motor.
IDK. So many different options and opinions on the subject... this website contains every piece of info you could ask for about these cars
http://www.vintage-mustang.com/