Change a mechanical instrument cluster to digital on an 89 firebird?

You need to rewire the entire car with a harness from a digital car. You have to remove the dash all the way to the firewall and replace with the digi dash and bezel. You'll need door latches from a digital car and the heater box needs to be from a digi, also. The heater control switch has to be changed to one from a digital car. It is a lot more than just pulling an analog cluster out and putting in a digital cluster. It's probably best to just get a digi car and restore it if you don't want a big project. Hope that helps!