The 87 and 88 headlight harnesses should be interchangeable. The 87 might have an extra wire, or pigtail, for a second horn. The 88 only has one horn.
However... The 87-88
4 cylinder front A/C harness (separate harness from the headlight harness) does not have the wires for the pressure/cycling switch that mounts on the receiver-dryer. It's replaced by a jumper in the connector. The interior harness for an A/C car does have the wiring, however.
I know you specified V6 harnesses, but that one got past me when I did my Duke to V6 swap. (Other than the engine harness, the front A/C harness is all the wiring I had to change. Failure to swap that harness will allow the compressor to kick on, even with no refrigerant, turning it into a doorstop in short order. Don't ask how I know this.
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[This message has been edited by Raydar (edited 06-20-2021).]
