You can change the front clip, taillights and dash and run the car as an older coupe that is in the classification guides as a turbo 4. Go to NHRA online and brows through the guides and pick a year.
http://www.nhra.com/tech_specs/class...ion/index.html
Mustang used the same body from 79 to 94 so changing years is easy,
Then go to the engine specs to make sure you have the right part numbers.
http://www.nhra.com/tech_specs/engine/index.html#ford
GOOD LUCK