FWIW,
As far as I recall after converting my non Rallye dash Instrument wire harness to a Rallye Dash harness:
The only thing I found different was that the Tach wire on rallye dashes was part of the original harnes.
Meaning that it was taped in with the rest of the bulk of harness. regardless of year, they were all the same except for the Tach wire.
Options like headlight reminder/courtesy, speaker upgrade options, light pkg. options, overhead, were added harnesses that branched off.