Hopefully you have schematics and routing diagrams.
I'd start with a visual inspection for bare wires or things touching that should not be. First look under the dash. If nothing is obvious, try looking at some of the things outside the instrument cluster that are lighted (transmission selector, etc.). If you still find nothing, pull the instrument cluster and look behind it.
If you see nothing, start disconnecting circuits until you find the one that casues the fuse to blow, then troubleshoot that circuit.