I bought an XR7 dash cluster for my 1968 standard Cougar. If I buy this wiring for the cluster can I make it work with my standard instrument wiring harness?
https://secure.cougarpartscatalog.com/store/p/12861-Socket-and-Wiring-Assembly-Instrument-Cluster-XR7-Used-1968-Mercury-Cougar.html?attribs=76
You will also need the XR-7 engine wiring harness and the sending unit for the oil gage, and the wiring to the RH dash.
The dash is not interchangeable. You really need to get the majority of an XR7 harness. What Royce is telling you is correct, but it is more than just the gauge feed harness you need, it is the harness that runs up the drivers side fender to the voltage regulator and then on around to the alternator. You will also need the correct alternator harness. The XR7 was an entirely different body code meaning that the differences started when the body was bucked. It is far easier to just put a tach in the clock location of a standard and call it a day.
Very involved process to change from a standard dash and wiring to an XR7. Different main wiring harness, different firewall to headlight harness, different engine feed harness, different alternator harness and console harness. Basically you change all the wiring other than rear tail light and fuel gauge harness. You would need the harness you selected from WCCC plus 5 others. If you have a standard car- the comment put a tach where the clock and keep the standard dash is the correct choice. A lot of labor and getting the harness’s is not easy or inexpensive to change all the pieces required.
If your just wanting the XR7 look you could pick up the dash and retrofit some aftermarket gauges into it, wiring wouldn’t matter as you would need to build your own for the gauges anyway. I have not done it but thinking it wouldn’t be to hard to modify the factory cluster to get aftermarket gauges in it, obviously involves cutting and modifying the backside but nothing much should change on the front side. There are some really nice aftermarket gauges out there, some even let you customize them to match your interior or overall look including text and logos on the faces.
Man now I kinda wanna do this!? Anyone got an XR7 dash they wanna sell? 
Thanks everybody! DieselD, yep the XR7 look is mostly what I’m looking for anyway. Probably will change the woodgrain look to a brushed aluminum too.
Their are aftermarket sellers of 67/68 dash panels with or without aftermarket gauge packages in a variety of finishes like brushed aluminum or carbon fiber on eBay and other sites. Probably a better way to go if someone wants to get the XR7 look. The original XR7 dash plastics are pretty fragile after 50+ years(and they have are pretty valuable as well). Would take some wiring for new gauges but still less than rewiring pretty much whole car.
Only one aftermarket option available as far as Im aware. Not sure how well the quality is however. From installed pictures they seem to be ok. 1967-1968 Mercury Cougar Dash Panel - Classic Dash
Still kinda like the idea of converting the xr7 stuff however
I posted this in another thread topic but it seems appropriate here as well.
Here’s what I did on my ‘68 convertible project:
https://cccforum.discoursehosting.net/t/g-for-sale/236/1
I wanted to keep my standard dash but give it an XR7 type of wood look. I also added a mini tachometer in the clock area.
The material is a plastic laminate used for sign engraving.
Steven
mr 580, I have seen those. Really nice but pricey. 1967 S Code, really nice job!