Instrument cluster

[jlcustomz]

If your more concerned with performance than factory original looks & can fabricate a little, Fitting an aftermarket tach into the stock assembly like the link I posted would cost less than $300 & perform better.
But your choice as to your wants & skills.

 

[Ringers]

That's a true statement. I for some unknown reason, get all bothered with the stock appearance stuff. The Aftermarket will be way more accurate, but I'm just building a nice tow rig and a dyno mule.

 

[Francisstark1]

I picked up a instrument cluster from a 85 montey carlo SS for a $150 in excelent condition with the wiring harness

 

[Longroof79]

Another factor that was not mentioned, is in many cases the wiring at the plug would have to be reconfigured to be compatible with the factory gauges.
It takes a small jewelers type screwdriver to release the connecting pins.
This write-up might help in that regard. http://www.maliburacing.com/gauge_conversion.html
Hope this helps.