Or...
You could pick up a SVO Engine, Comp and Wiring from another SVO Stang of TC for about $500'ish, maybe less.
Where i live in IL, you can find 5.0 engines for about $200 too.
You could also change the cam, headers (Ranger headers), Intake (again from a Ranger) and CAI/WAI but thats about it. The 2.3 N/A's were not designed from HP, only fuel economy. Im guesing you have the DIS system too.
I wouldnt waste the money modding your N/A unless you plan on a rebuild with better pistons and all.
Theres ALOT of info out there on engine swaps for these cars.