[jp2code]

The manual transmission doesn't have a wiring harness. It's got a Reverse Switch, a Neutral Switch, and a Speedometer Sensor.

The 85 manual probably uses a Speedometer Gear, so you'll have to swap it with your Speedometer Sensor - but they go in the same hole, so you should be OK.

 

[jp2code]

Do I have to change the entire body harness or are they the same and I just had to change the ECU in the engine harness

I don't know. There aren't many write-ups about this.