I have an 88 and found that changing out the radiator system form the 88 era to the 92 era worked out very well.
I purchased a three pass radiator (instead of the two pass factory install in the 88 era's) and changed out the heater valve too. It makes a great difference to your air conditioner and heater system.
There are many links listed in Automotiveforums.com
Hope this helps.