I'm assuming its a 6 cyl since its in this forum. First thing I would do is get some headers, and H-pipe and convert to duel exhaust. That will give you some perforemance gain! Then I would get underdrives pulleys and a cold air induction kit. You could always swap put the gears and go with a steeper gear for better acceleration that the 6 cyl's need. Go to
Mustangs Unlimited and they have a parts you might be interested in. Also check out
Racer Walsh