I'm currently redoing my 67 dash harness, so I know there are differences between 67 thru 9 cudas. All have subtle 1 year only differences, and that includes the wiring. See pics here of 67 headlight switch connector(different than 68). And the headlight dimmer switch. Wire colors are different.
*** in Headlight switch connector ** the pink wires are doubled. Pic doesnt show it tho.