Any 85 - 88 harness is going to be about the same as far as a donor harness for a 3800 conversion is concerned. 87-88 4 cylinder Fieros had a second connector near C203 for the cruise if that makes a difference for you. None of V6 or the earlier 4s had the separate cruise connector.
88 4s and 6s do have the newer type oil pressure connector however it is a 3 pin oil pressure connector. I recommend a 4 pin connector instead and using the 4 pin Bonneville oil pressure sender since it won't peg the oil pressure gauge.