Installing 88 engine in 83 chassis
 

Just did this a few days ago, so posted experience here. Obviously, if you are not installing 88 ECU and AFM, you can use your old harness and there is nothing to write about. But the later ECU does give some additional benefits.

Kevin Gosselin: Installing 88 Engine in 83 944. Solving Wiring Issues.

Wow,thanks heeps ,I did 89 motor into 85 car,now I can get my tach going,cheers

Tach wiring?
 

Sorry to be a pain but I'am a little confused about the tach wiring part of your article,I don't have a merging wire between #2 and #4 on my old 1985 (Series 1) harness,I do have a single green/black in #4 position however.
I have a double connector hanging under the dash below the tach (green/black and black wires) do I run separate wiring to these from the harness plug green/black to green/black and black to black? will that work?,thank you.