With NX1600 digital clusters becoming prohibitively expensive and rare, is it possible to retrofit any other Nissan cluster onto a 180sx? The Z31 and the Maxima clusters are the first ones that come into my mind when considering alternatives to the NX1600. Can any other members chime in with their experience and let me know what is possible?

Technically you could put whatever cluster you want in the dash, as long as you can manage fitment. And as long as you splice the dash wires into the right pinouts for the new cluster you should be good.

Another thing you may want to do is find how much voltage the new cluster needs, since you may need to use resistors.