I purchased a cluster from a 2012 FZ6R (they are the same as the 2nd gen FZ6 clusters). The FZ8 and FZ1 clusters should also work, the FZ8 one just has a white face instead of black.
Since the 1st gen FZ6 cluster has two connectors on the back, and the 2nd gen cluster has 1 connector, the easiest thing to do is to get the front section of the wiring harness from a 2FZ6 or FZ6R. The 2 connectors on the back of the harness that connect to the main harness are the same in the 1FZ6, 2FZ6, FZ6R. Your 1 connector now works with your new cluster. It's plug and play. Everything worked exactly as intended on my new gauge. The only thing is your odometer will be incorrect, naturally.