From what i can tell the wiring diagrams are the same for the cor however when shopping for the part it does not list the 89 gtus as a compatible vehicle with the part. Can anyone verify that the cor is indeed the same for all fc's?

 

I've never seen anything to indicate otherwise; it's just a relay. Where are you shopping for the replacement? I wouldn't be surprised if an general auto parts store didn't know the GTUs model existed.

 

not able to find it at any stores, just on ebay.