I did it to my 91. You need a dizzy, the head.and intake. Use the newer throttle body, and you have to do some pinning to plug the dizzy in. its not a bad job, i figured it out myself in high school with some wiring diagrams.
The big advantage you get from this conversion, which does not require a computer change, is the ease of timing advance change. Without a tuner it is unchangable with the 8 plug. The 4 plug intake and head are better for performance (i think) than the 8.
All of the 2.3 heads from our engine family will fit your engine block, including the 2.5L Ranger. Other than the Esslinger SVO head RACE ENGINEERING - Cylinder Head - 2300 - 2500 - 2700 - 2850 - Race Engineering, Inc and the Race engineering head, the castings I like the most are the last single plug castings, available on Mustangs, 87'-90. Ironically, they don't flow that much in stock form, but a few hours with a rotary file, can make a huge difference with them.
Here's what the un-ported airflow looks like on the 87'-90 casting I recently tested.
You can use a head from a ranger up to 2001. After that the changed engines. There is not a diagram that can be used specifically for this conversion. I do however have the diagrams, and pin locations to do it, i have already went through this somewhere in these forums, if you look around its there. Also, any head from 88-on ranger and 91-on mustang will not be compatible with a distributor. they are all 8 plug and the intakes et in the way of the distributor.