Any mods I could do to my 2.3L 89 mustang?
Try to find either a Merkur 2.3, turbo-bird, or turbo cougar set up.
The engine is easy to turbo charge. But look for the fuel injected models.
There are other cams for this. Racer Walsh has one of the best sites to get upgrade parts.
Make sure that you use an inter-cooler. One that mounts in front of the radiator is preferred.
Just a different cam would help, and roller cams. These parts swap in from newer models.
Also Speedway motors has some speed parts for this engine (mini-stock section).
This engine can be made to rip. I had one in a Mustang II that could take a V-8 model Camaro.
There are a lot of tricks out there.