Will need cluster and dash wiring
Cluster along with wiper switch, since standard cluster wiper switch is longer and won't fit on the Rallye cluster location ( will meet with internal dash areas ). Light switch is the same.
Knobs also changes. Be sure to get it with those. Most of Rallye clusters around got missed the wiper knob.
Depending on your skills you could make to work your standard cluster wiring into the Rallye cluster setup. Rallye cluster gets sockets and wires to reach every location, diff than Standard cluster which gets a multipin conector to a PCB.
Recommendation... get a 73 harness. EVERY YEAR is diff for some reason. The closer between them is 72 and 73 where would need to still check the bulkhead wiring disposition ( could need to swap couple of wires ).
The most diff is the 74.
71 is also diff for several reasons.
There are 2 kind of Rallye cluster with 3 variations.
The basic one
And the one with clock or Tach, either one, cluster is the same but the gauge interchange.
These both kind of cluster gets a diff housing, gauge meters and lense mask and don't interchange between them. Well, you can phisically fit the lense mask but won't match the gauges disposition. Allong with the hole for the clock adjuster shaft. Wood grain bezel is not affected about this thought!
Housing is actually also molded/casted for both cluster dispositions thought, but still drilled and cut for one or the other setup.
All 71/72 are 150 speedos. 73/74 are most of them 120 speedos ( first one I posted is 74 with 120 speedo ), but you still can find some with 150 speedos ( most of them on 73 clusters ). Speedos are interchangeable thought.
Another cluster minor differences
74 speedo get a blue lense for high beams, rest are red.
71 speedos get a vertical notch for high beams indicator, while laters are horizontal
74 bezel get extra icons to indicate switch functions ( you can see them on the first pic I posted ) while the rest not.
71 wiper switch is diff from 72/74 so the plug for it on harness changes. Wiring is the same thought
A/C-heater controls are diff between 71/72 and 73/74 not just on How it looks but also on some plugs on back, BUT you can fit your own unit with the harness. A/C-Heater harness separates easily from underdash harness to fit on the harness you get.
About harness, most of differences are related to seatbelt warning system: buzzers, indicators, sensors, control relays... this make to change several parts of the harness itself. Just 72 and 73 shares this setup being the same, hence why these are the best to switch between them.