The stock driveshaft will work.
You will need:
1. Cut spot welds off x-member so you can adjust the x-member to line up with transmission.
2. Shifter (Hurst, Cheetah, B&M, etc.)
3. Bellhousing (I suggest 157T) Smaller to fit in the tunnel (JW makes a nice bell)
4. Flexplate (if stock 50 oz. other whatever your motor is balanced at) (TCI, Performance Automatic, etc.)
5. Convertor (If going 157T go with a 10.5 Bolt circle) I would talk with a trans company like Dynamic, Redneck, Coan, TCI, Performance Automatic, PTC, etc to get a convertor for your particular application)
X275 build in progress follow on Mustang Junkies.net