With the 5.0L in the 94/95 GT's you could always buy the Holley Systemax kit or Edelbrock kit or whatever. In MM&FF a car with the Edel kit ran a 13.5 with exhaust, gears, and drag radials.
The systemax kit goes for around $2000 and gears and exhaust you might get for around $1000. That would put you in the low to mid 13's no problem.
Buy the MM&FF 5.0 Tech guide and read it.
------------------
1995 Mustang GT