switching wiring harness

Do anybody know the difference between the 67 to 69 and the 70 to 72 wiring harness.I have a engine wiring harness from a 70 A body and want to use it on a 67 barracuda. Can I just plug it into the 67 harness block or do I need the wiring harness from the inside of the car also.I want to use the 70 and up regulator on my 67.Also I would rather cut up a 70 harness then a 67 rally dash harness.I do have both. I don,t need any of the wires going to the dash except to the heater{I am doing a custom dash}.I know the ignition switch wires I need to change. Mark