I agree with Bob. The FZJ80 weighs around 5000 lbs with a full load of liquids and with cargo and 4-5 adults will go close to 6000 lbs. so you have the 1.5X multiplier that most "experts" recommend.
I'd consider that a minimum so the snatch block is a must have to give you some additional oomph! You probably will want to avoid extended heavy pulls because with a heavier vehicle you'll be running the winch closer to peak load.
On the other hand, you can do a lot of expensive damage if you aren't careful using a 12000 lb winch. Lookout if you hook a snatch block to a 12k reel and take shortcuts with your anchor, angles or attachment points!
I've bought 4 winches, and the first two of those purchases resulted in buyer's remorse because I "got a deal" and it turned out I really needed the stronger but more expensive winch. Just something to keep in mind, avoid the siren song of a sale unless the winch that you really want happens to be on sale.