i was wondering what i would have to do change my 89' 2.3 to a police intercepter if i already have the motor and trans

 

First off: "Police Interceptor" tells us nothing; it's a generic term for a cop car motor.
Is it a 5.0 or a 4.6?
What transmission will you be using? 4 banger T5, V8 T5, or ?
Are you going fuel injected or carb'd?